[core] implement support for run-time dependency version checking

[stas00]

As discussed at #8073 (comment) this PR:

• adds mechanics for run-time dependency version checks (module with fixed and unversioned too)
• adds thorough tests (this is where it's the easiest to see how things work)
• creates one source for all dependency versions in setup.py - need to rerun setup.py on its update to re-generated src/transformers/dependency_versions_table.py, which is then used by transformers
• adds support and deploys python runtime version check
• deploys runtime checks for versioned modules in setup.py's install_requires (i.e. must modules)
• switches examples/lightning_base.py to a fatal-on-failure requirement check.
• deploys the version lookup setup.py's extras definitions and install_requires
• adds new Makefile target deps_table_update that updates the dep table, and inserts it into style/quality/fixup targets so the sync shouldn't take too long if forgotten to be run explicitly

@sgugger, @LysandreJik, @patrickvonplaten, @thomwolf

[patrickvonplaten]

This is a great addition and I think will save us from a lot of repetitive version mismatch issues - thanks a lot @stas00 !

Two things:

• I don't think tokenizers is a mandatory dependency
• Not sure if need this functionality to write a dependency table file. Curious to hear your thoughts here though!

[stas00]

@sgugger, wrt your comment in your announcement

=> Resulting breaking change: some people will have to install sentencepiece explicitly while they didn’t have to before with the command pip install transformers[sentencepiece].

After this PR, you can just require_version("sentencepiece", "pip install transformers[sentencepiece]") in the code that needs it at run-time. You can expand the hint (second arg) as you wish to be self-explanatory.

[stas00]

@LysandreJik and @sgugger - it's ready to merge whenever you have a chance to review. Thank you.

Probably it is best to merge post v4-release, in case I missed something.

[sgugger]

Will do a final review tomorrow!

[sgugger]

Very nice! Could you please pass the new parts of the setup.py though the formatter? There are some inconsistencies with the rest of the library (using single quotes instead of double quotes, dicts have weird spacing). Thanks!

[LysandreJik]

This is great. Thank you for your work on this Stas.