Add `ArrayShardedExt::effective_inner_chunk_shape`

[LDeakin]

Fixes the inner chunk grid calculation for the case where the transpose codec precedes sharding_indexed

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 95.91837% with 4 lines in your changes missing coverage. Please review.

Project coverage is 82.09%. Comparing base (7fa0c43) to head (6008d69). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ay/codec/array_to_array/bitround/bitround_codec.rs	0.00%	3 Missing :warning:
.../codec/array_to_array/transpose/transpose_codec.rs	92.30%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #70 +/- ## ========================================== + Coverage 81.65% 82.09% +0.43% ========================================== Files 163 163 Lines 22242 22341 +99 ========================================== + Hits 18162 18340 +178 + Misses 4080 4001 -79 ```

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