fix: schema conversion, add conversion test cases

[ion-elgreco]

Description

With the refactor I introduced a minor bug, but it's only fixable with an upstream change in arro3, kylebarron/arro3#334. cc @kylebarron

I already have the new code stashed locally, so once arro3 is released I will push those changes and it should work ✨

The conversion test cases will highlight the issue for lists that lose the name, nullability and metadata ^^

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 71.23%. Comparing base (226c397) to head (616b352).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
python/src/lib.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3468      +/-   ##
==========================================
+ Coverage   71.21%   71.23%   +0.01%     
==========================================
  Files         149      149              
  Lines       44825    44825              
  Branches    44825    44825              
==========================================
+ Hits        31922    31930       +8     
+ Misses      10831    10828       -3     
+ Partials     2072     2067       -5     

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[roeap]

just some general comments we may want to look at for 1.0.

[roeap]

aside: could we mark this as experimental as well for 1.0?

Not sure where this will end up, but there are two things 1) we can get rid of much of the flattening code by using RecordBatch::normalize(".") and 2) we currently generate this from add actions, but should move to using record batches we read from the log directly.

The new approach might be to expose a schema and the batches ? in the end though I think this is how we should expose actions, but may want to change the schema of the returned data.

[ion-elgreco]

But we haven't for all the previous releases, wouldn't that be strange to mark it experimental now. I think we can still deprecate changes beyond 1.0.0