Adding test presets for mms + support for any encoder in reference model

[gilkeren1]

What does this PR do? Please describe:
As discussed in the meeting, adding two test presets for mms that can be quickly run (10 mins) to verify PRs are not breaking training. One preset for llm-asr and another for ctc.

those two tests are passing right now:
test_ctc_seed2_test_presets
test_llm_asr_seed2_test_presets

Fixes #{issue number}
n/a

Does your PR introduce any breaking changes? If yes, please list them:
No

Check list:

• Was the content of this PR discussed and approved via a GitHub issue? (no need for typos or documentation improvements)
• Did you read the contributor guideline?
• Did you make sure that your PR does only one thing instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests?
• Did you verify new and existing tests pass locally with your changes?
• Did you update the CHANGELOG? (no need for typos, documentation, or minor internal changes)

All ok

[artemru]

why this vocab size ? can you leave a comment ?