feat: expose arrow schema on snapshots

[roeap]

Description

In many places we require the arrow schema of a snapshot. As such we replicate converting schemas in many places. In this PR we track a reference to an arrow schema on our innermost snapshot and start using it in some places.

We also now expose the kernel schema as an arc to better alogn with how delta kernel and datafusion expose schemas.

part-of: #3733

[codecov]

Codecov Report

❌ Patch coverage is 81.13208% with 30 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.38%. Comparing base (d5402ee) to head (4bc9c40).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/core/src/delta_datafusion/mod.rs	71.11%	9 Missing and 4 partials ⚠️
python/src/schema.rs	0.00%	5 Missing ⚠️
crates/core/src/kernel/snapshot/mod.rs	90.00%	0 Missing and 3 partials ⚠️
python/src/lib.rs	0.00%	3 Missing ⚠️
crates/core/src/delta_datafusion/cdf/scan.rs	0.00%	1 Missing ⚠️
crates/core/src/operations/add_column.rs	0.00%	1 Missing ⚠️
crates/core/src/operations/load.rs	0.00%	0 Missing and 1 partial ⚠️
crates/core/src/operations/merge/mod.rs	94.44%	0 Missing and 1 partial ⚠️
crates/core/src/operations/optimize.rs	50.00%	0 Missing and 1 partial ⚠️
python/src/query.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3822      +/-   ##
==========================================
+ Coverage   74.34%   74.38%   +0.04%     
==========================================
  Files         147      147              
  Lines       39517    39522       +5     
  Branches    39517    39522       +5     
==========================================
+ Hits        29377    29397      +20     
+ Misses       8740     8739       -1     
+ Partials     1400     1386      -14     

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[roeap]

@ion-elgreco - there was some confusion with the arrow_schema field on the datafusion mixin. this is fixed now and we also made the schema methods on the mixin infallible.

mind stamping again? 😄