perf: Improve performance of Chart.from_dict

[RobinL]

Closes #3382

This PR substantially improves performance of alt.Chart.from_dict. See #3382 for a detailed description and reprex.

Grateful for any feedback on this PR, e.g. whether the team would prefer I leave the current function as is, or use functools.lru_cache, instead of the top-level jsonschema_version_str = importlib_version("jsonschema") statement. Or some other solution.

WIP whilst I make sure the builds/tests pass

[jonmmease]

Thanks for the investigation and the fix @RobinL! I think this is a reasonable way to go, but would like to hear from @binste as well

[RobinL]

Thanks very much for the quick response, will await feedback from binste.

[Edit - apologies for the force push, had accidentally committed the schemapi.py from utils rather than tools]

[jonmmease]

This is straightforward enough that with the passing tests I'm fine merging it. We can make any adjustments before the 5.3.0 release if anyone want to weight in afterward.

[binste]

Nice catch @RobinL! Thanks for finding and fixing it :)

Thanks Jon for the review! Fully agree, changes look good so we can release it in 5.3.0 as-is.