Update paddings

[HamidShojanazeri]

What does this PR do?

This PR adds the update for padding with new tokenizer changes which requires change in embedding size.

Fixes # (issue)

Feature/Issue validation/testing

Please describe the tests that you ran to verify your changes and relevant result summary. Provide instructions so it can be reproduced.
Please also list any relevant details for your test configuration.

• Test A
  Without resizing the embedding after adding Pad token, error_logs

• Test B
  With resizing the embedding after adding Pad token https://gist.github.com/HamidShojanazeri/3e9030419044104988795c9b1bce6e44

Before submitting

• [ X] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline,
  Pull Request section?
• [ X] Was this discussed/approved via a Github issue? Please add a link
  to it if that's the case.
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

Thanks for contributing 🎉!

[chauhang]

@HamidShojanazeri Thanks for this PR. Please add documentation updates explaining the usage and in which scenario padding will be needed. At present a bunch on new warning messages are getting printed based on the values passed for the max_padding_length parameter and no change in the generated output.