[OpenVINO] Set Left Padding For Text Generation Task

[apaniukov]

What does this PR do?

Set the left padding side during tokenizer conversion for text generation tasks.

Fixes # (issue)

Before submitting

• [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• [ ] Did you make sure to update the documentation with your changes?
• [x] Did you write any new necessary tests?