Datatype deduplication 1: remove polars

[teh-cmc]

All the grunt work left to get rid of polars.

• Remove all helpers and APIs built specifically for polars' DataFrame.
• Refactor tests that rely on dataframe joins to not require join semantics in the first place (re_data_store has no knowledge of those anyway).
• The one test that does require join semantics has moved over to re_query, where join semantics belong.
• All polars-* dep have been removed.

Don't look at the commit log as it makes no sense: i changed strategies a bunch of times on the way.

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• Part of Fork arrow2 and get rid of polars #4789
• DNR: requires Primary caching 19 (final): de-staticify cache globals #4856

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Part of the tiny datatype deduplication PR series:

• Datatype deduplication 1: remove polars #4880
• Datatype deduplication 2: switch to re_arrow2 #4883

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[emilk]

YAY! :D

[emilk]

The above code would be more idiomatic using std::sync::Once.

It could also be moved into setup_native_logging

[teh-cmc]

Yeah i've told myself I'd clean this a million times... I'll do so in a follow up.

[teh-cmc]

• setup_native_logging needs to handle its own Once semantics #4893