adding max_token_capacity metric

[Edwinhr716]

What does this PR do?

Emit max_batch_total_tokens as max_token_capacity as part of metrics standardization

Fixes # (issue)

Before submitting

• [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• [X] Did you read the contributor guideline, Pull Request section?
• [X] Was this discussed/approved via a Github issue or the forum? Please add a link to it if that's the case. This has been discussed in #1977, as part of metric standardization
• [ ] Did you make sure to update the documentation with your changes? Here are the documentation guidelines, and here are tips on formatting docstrings.
• [ ] Did you write any new necessary tests?

Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag members/contributors who may be interested in your PR.