fix: make ScalarValue::eq_array match float PartialEq

[shinzoxD]

Which issue does this PR close?

• Closes ScalarValue::eq_array is inconsistent with ScalarValue equality for floating-point values #24431

Rationale for this change

ScalarValue::eq_array is documented as an optimized equivalent of extracting an array element with try_from_array and comparing the resulting scalars. For floating-point values this was not true: eq_array used IEEE equality while ScalarValue::PartialEq compares bit patterns.

That produced inconsistent results for hash-table key comparisons and any other caller of eq_array:

• Identical NaN bit patterns compared equal as ScalarValues but unequal through eq_array.
• +0.0 and -0.0 compared unequal as ScalarValues but equal through eq_array.

Changing PartialEq to IEEE equality would break Eq reflexivity for NaNs and require coordinated hash/order changes. The correct fix is for eq_array to match the existing PartialEq contract.

What changes are included in this PR?

• Compare Float16, Float32, and Float64 in eq_array using to_bits(), matching ScalarValue::PartialEq.
• Document the bit-pattern equality semantics on eq_array.
• Add unit tests for NaN payloads and signed zeros on all three float widths.

Are these changes tested?

Yes. test_eq_array_float_nan_and_signed_zero checks that eq_array matches try_from_array + PartialEq for Float16/32/64, including:

• identical NaN bits are equal
• distinct NaN payloads remain unequal
• +0.0 and -0.0 remain distinct
• nulls and ordinary values still compare correctly

Without the to_bits() change the new test fails (identical NaN: eq_array false vs PartialEq true).

Are there any user-facing changes?

Yes. Callers of ScalarValue::eq_array on floating-point values now get the same results as ScalarValue::eq. This is a behavior fix for the documented API contract; PartialEq itself is unchanged.

No documentation site updates are needed beyond the rustdoc note on eq_array.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[Jefffrey]

we have a PR for this

• fix: expand float fuzz coverage and correct discovered inconsistencies #24433

[Jefffrey]

for anyone looking at this PR please see my comment here:

• fix: roll back DiskManager usage when spill write I/O fails #24407 (comment)