[GPU] Init tensor.data when allocating inputs for string type

[davidsnam-intel]

Details:

• In case the element type is string produces the segmentation fault when input data is an empty string, unless the each element of tensor.data is initialized.

Tickets:

• 148921

[p-wysocki]

All plugins handle empty strings without throwing but GPU, and this PR adds an additional if check for every string on all plugins. It's a high level fix for a low level issue.

Still, it's a fix for an existing issue, so I approve under the condition that is an additional story or discussion on what the desired plugin behavior for empty string is and adjust GPU if necessary.

[akuporos]

I'd also expect to see the fix in GPU plugin directly, not in Python API.
As it was described in the ticket by @p-wysocki, the problem is GPU-specific, CPU works well.

GPU implementation was fixed to resolve the issue.