refactor(rust): Refactor hist

[mcrumiller]

I'd like to move towards addressing #23272, but we need an integer-specific implementation of hist for this to work, as the large-integer timestamps in us and ns work pretty poorly when converted to floats in the current histogram implementation. This refactor is intended to allow for easier paths for more dtype-specific histogram implementations if desired. The base algorithms remain the same, but there is a slightly better distinction between variable-width histograms (i.e. user-supplied edges) and uniform-width histograms (bin-count supplied).

I've moved the cast of the series and bins to the IR to make the implementation a little cleaner by the time we reach it. If we move to temporal histograms, we can easily coerce the arguments in the IR as well so that supplied bins match the series.

At some point soon, I would like to rename bins to edges (open issue #23335), since the parameter actually refers to the bin edges, not the bins themselves. Internally we now use edges as it's much clearer what it refers to.

No changes to tests, as they are fairly comprehensive.

[codecov]

Codecov Report

❌ Patch coverage is 96.98276% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.61%. Comparing base (dc6f1ad) to head (fb3ed94).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-ops/src/chunked_array/hist.rs	97.39%	5 Missing ⚠️
...ars-plan/src/plans/conversion/type_coercion/mod.rs	95.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #25574      +/-   ##
==========================================
- Coverage   79.71%   79.61%   -0.11%     
==========================================
  Files        1729     1729              
  Lines      239702   239771      +69     
  Branches     3038     3038              
==========================================
- Hits       191078   190891     -187     
- Misses      47841    48097     +256     
  Partials      783      783              

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