Add versioning to MTEB benchmarks

[KennethEnevoldsen]

• Following suggestion made in Rename MTEB(eng) & MTEB(eng,classic) #2001 I added version to MTEB benchmarks
• changed the name of the MTEB(Chinese) to MTEB(cmn, v1). Though we could go for MTEB(Chinese, v1) assuming it is a group (also covering chinese other than mandarin)
• change the name of FaMTEB(fas, beta) to MTEB(fas)
• did a minor formatting of imports due to a circular import error
• moved the Benchmark object out of the file with the benchmarks
  • this is still >1000 lines so we could split it up to "external_benchmarks", "monolingual_benchmarks", "domain_specific_benchmarks", "multilingual_benchmarks"

Fixes #2001

Code Quality

• Code Formatted: Format the code using make lint to maintain consistent style.

Documentation

• Updated Documentation: Add or update documentation to reflect the changes introduced in this PR.

Testing

• New Tests Added: Write tests to cover new functionality. Validate with make test-with-coverage.
• Tests Passed: Run tests locally using make test or make test-with-coverage to ensure no existing functionality is broken.

[Muennighoff]

Nice! To avoid breaking backward compat would it make sense to temporarily allow the old names by just mapping to the new benchmark carrying that name and raising a warning that the old name will be deprecated soon?

[KennethEnevoldsen]

Nice! To avoid breaking backward compat would it make sense to temporarily allow the old names by just mapping to the new benchmark carrying that name and raising a warning that the old name will be deprecated soon?

Good catch, will add this tomorrow

[x-tabdeveloping]

I agree with Niklas, Also make sure this doesn't break the leaderboard (I think it probably will since the multilingual benchmark is referred to by name)

[KennethEnevoldsen]

I have added changed for backward compatibility. I have also updated the leaderboard code to refer to the MTEB_multlingual.name. This should prevent inconsistencies.