TEST: Reduce redundant numerical test matrices

[vyasr]

Description

Replace covariance/correlation’s redundant operand Cartesian product with nine explicit representative pairs, and remove an unused parameter from one masked-binary execution test.

Coverage accounting

• The pairs retain normal and integer inputs, constant and all-null values, nullable arrays, Arrow input, empty input, and singleton input.
• The indexed-Series pair uses the same three labels in a different order on both sides, retaining multi-row index-alignment behavior rather than only a singular/NaN outcome.
• The same pairs run for covariance and both Pearson and Spearman correlation (189 items to 27).
• The removed extension-compilation type parameter was not consumed by the test: every former node executed the same integer-scalar kernel.

Checklist

• I am familiar with the CONTRIBUTING.md guidelines.
• New or existing tests cover these test-only changes.
• Documentation updates are not needed.

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[vyasr]

/ok to test

[vyasr]

/ok to test