[ONNX] Fixed wrong type casting for u/int16 when it stored externally (…

…#28016)

### Details:
 - Fixed wrong type casting for u/int16
- Added more tests for correctness validation of a values from external
file

### Tickets:
 - 159142

src/frontends/onnx/frontend/src/core/tensor.hpp

@@ -313,7 +313,7 @@ class Tensor {
         } else {
             buffer = ext_data.load_external_data(m_model_dir);
         }
-        return std::vector<T>(buffer->get_ptr<char>(), buffer->get_ptr<char>() + buffer->size());
+        return std::vector<T>(buffer->get_ptr<T>(), buffer->get_ptr<T>() + (buffer->size() / sizeof(T)));
     }
 
     const void* get_data_ptr() const {

src/frontends/onnx/tests/models/external_data/external_data_int16.prototxt

@@ -0,0 +1,75 @@
+ir_version: 3
+producer_name: "OpenVINO ONNX Frontend"
+graph {
+  node {
+    input: "A"
+    input: "B"
+    output: "Y"
+    name: "add_node1"
+    op_type: "Add"
+  }
+  name: "test_graph"
+  initializer {
+    dims: 2
+    dims: 2
+    data_type: 5
+    name: "A"
+    external_data {
+        key: "location",
+        value: "tensors_data/tensor.data"
+    }
+    external_data {
+        key: "length",
+        value: "8"
+    }
+    data_location: 1
+  }
+  input {
+    name: "A"
+    type {
+      tensor_type {
+        elem_type: 5
+        shape {
+          dim {
+            dim_value: 2
+          }
+          dim {
+            dim_value: 2
+          }
+        }
+      }
+    }
+  }
+  input {
+    name: "B"
+    type {
+      tensor_type {
+        elem_type: 5
+        shape {
+          dim {
+            dim_value: 1
+          }
+        }
+      }
+    }
+  }
+  output {
+    name: "Y"
+    type {
+      tensor_type {
+        elem_type: 5
+        shape {
+          dim {
+            dim_value: 2
+          }
+          dim {
+            dim_value: 2
+          }
+        }
+      }
+    }
+  }
+}
+opset_import {
+  version: 4
+}

src/frontends/onnx/tests/models/external_data/external_data_int4.prototxt

@@ -0,0 +1,65 @@
+ir_version: 3
+producer_name: "OpenVINO ONNX Frontend"
+graph {
+  node {
+    input: "A"
+    output: "Y"
+    name: "add_node1"
+    op_type: "Identity"
+  }
+  name: "test_graph"
+  initializer {
+    dims: 2
+    dims: 2
+    data_type: 22
+    name: "A"
+    external_data {
+        key: "location",
+        value: "tensors_data/tensor.data"
+    }
+    external_data {
+        key: "offset",
+        value: "2"
+    }
+    external_data {
+        key: "length",
+        value: "2"
+    }
+    data_location: 1
+  }
+  input {
+    name: "A"
+    type {
+      tensor_type {
+        elem_type: 22
+        shape {
+          dim {
+            dim_value: 2
+          }
+          dim {
+            dim_value: 2
+          }
+        }
+      }
+    }
+  }
+  output {
+    name: "Y"
+    type {
+      tensor_type {
+        elem_type: 22
+        shape {
+          dim {
+            dim_value: 2
+          }
+          dim {
+            dim_value: 2
+          }
+        }
+      }
+    }
+  }
+}
+opset_import {
+  version: 21
+}

src/frontends/onnx/tests/models/external_data/external_data_int8.prototxt

@@ -0,0 +1,75 @@
+ir_version: 3
+producer_name: "OpenVINO ONNX Frontend"
+graph {
+  node {
+    input: "A"
+    input: "B"
+    output: "Y"
+    name: "add_node1"
+    op_type: "Add"
+  }
+  name: "test_graph"
+  initializer {
+    dims: 2
+    dims: 2
+    data_type: 3
+    name: "A"
+    external_data {
+        key: "location",
+        value: "tensors_data/tensor.data"
+    }
+    external_data {
+        key: "length",
+        value: "4"
+    }
+    data_location: 1
+  }
+  input {
+    name: "A"
+    type {
+      tensor_type {
+        elem_type: 3
+        shape {
+          dim {
+            dim_value: 2
+          }
+          dim {
+            dim_value: 2
+          }
+        }
+      }
+    }
+  }
+  input {
+    name: "B"
+    type {
+      tensor_type {
+        elem_type: 3
+        shape {
+          dim {
+            dim_value: 1
+          }
+        }
+      }
+    }
+  }
+  output {
+    name: "Y"
+    type {
+      tensor_type {
+        elem_type: 3
+        shape {
+          dim {
+            dim_value: 2
+          }
+          dim {
+            dim_value: 2
+          }
+        }
+      }
+    }
+  }
+}
+opset_import {
+  version: 4
+}

src/frontends/onnx/tests/models/external_data/external_data_uint16.prototxt

@@ -0,0 +1,75 @@
+ir_version: 3
+producer_name: "OpenVINO ONNX Frontend"
+graph {
+  node {
+    input: "A"
+    input: "B"
+    output: "Y"
+    name: "add_node1"
+    op_type: "Add"
+  }
+  name: "test_graph"
+  initializer {
+    dims: 2
+    dims: 2
+    data_type: 4
+    name: "A"
+    external_data {
+        key: "location",
+        value: "tensors_data/tensor.data"
+    }
+    external_data {
+        key: "length",
+        value: "8"
+    }
+    data_location: 1
+  }
+  input {
+    name: "A"
+    type {
+      tensor_type {
+        elem_type: 4
+        shape {
+          dim {
+            dim_value: 2
+          }
+          dim {
+            dim_value: 2
+          }
+        }
+      }
+    }
+  }
+  input {
+    name: "B"
+    type {
+      tensor_type {
+        elem_type: 4
+        shape {
+          dim {
+            dim_value: 1
+          }
+        }
+      }
+    }
+  }
+  output {
+    name: "Y"
+    type {
+      tensor_type {
+        elem_type: 4
+        shape {
+          dim {
+            dim_value: 2
+          }
+          dim {
+            dim_value: 2
+          }
+        }
+      }
+    }
+  }
+}
+opset_import {
+  version: 4
+}

src/frontends/onnx/tests/models/external_data/external_data_uint4.prototxt

@@ -0,0 +1,65 @@
+ir_version: 3
+producer_name: "OpenVINO ONNX Frontend"
+graph {
+  node {
+    input: "A"
+    output: "Y"
+    name: "add_node1"
+    op_type: "Identity"
+  }
+  name: "test_graph"
+  initializer {
+    dims: 2
+    dims: 2
+    data_type: 21
+    name: "A"
+    external_data {
+        key: "location",
+        value: "tensors_data/tensor.data"
+    }
+    external_data {
+        key: "offset",
+        value: "2"
+    }
+    external_data {
+        key: "length",
+        value: "2"
+    }
+    data_location: 1
+  }
+  input {
+    name: "A"
+    type {
+      tensor_type {
+        elem_type: 21
+        shape {
+          dim {
+            dim_value: 2
+          }
+          dim {
+            dim_value: 2
+          }
+        }
+      }
+    }
+  }
+  output {
+    name: "Y"
+    type {
+      tensor_type {
+        elem_type: 21
+        shape {
+          dim {
+            dim_value: 2
+          }
+          dim {
+            dim_value: 2
+          }
+        }
+      }
+    }
+  }
+}
+opset_import {
+  version: 21
+}