ci: Lock dependencies for python-level tests

Examples/Python/tests/requirements.in

@@ -0,0 +1,4 @@
+pytest
+pytest-check
+uproot
+awkward

Examples/Python/tests/requirements.txt

@@ -1,4 +1,37 @@
-pytest
-pytest-check
-uproot
-awkward
+#
+# This file is autogenerated by pip-compile with python 3.9
+# To update, run:
+#
+#    pip-compile requirements.in
+#
+attrs==21.4.0
+    # via pytest
+awkward==1.7.0
+    # via -r requirements.in
+iniconfig==1.1.1
+    # via pytest
+numpy==1.22.2
+    # via
+    #   awkward
+    #   uproot
+packaging==21.3
+    # via pytest
+pluggy==1.0.0
+    # via pytest
+py==1.11.0
+    # via pytest
+pyparsing==3.0.7
+    # via packaging
+pytest==7.0.1
+    # via
+    #   -r requirements.in
+    #   pytest-check
+pytest-check==1.0.4
+    # via -r requirements.in
+tomli==2.0.1
+    # via pytest
+uproot==4.1.9
+    # via -r requirements.in
+
+# The following packages are considered to be unsafe in a requirements file:
+# setuptools