refactor(bigframes): Introduce GoogleSqlScalarOp

[TrevorBergeron]

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Fixes #<issue_number_goes_here> 🦕

[gemini-code-assist]

Code Review

This pull request introduces GoogleSqlScalarOp to provide a more direct mapping between BigFrames operations and GoogleSQL functions, refactoring several geography and mathematical operations to use this new infrastructure. It also adds support for omitted optional arguments across the expression and compilation layers for both Ibis and sqlglot. Feedback identifies several critical implementation errors in the Ibis compiler registry, including incorrect list methods, return type mismatches, and logic errors in argument indexing. Additionally, there are issues with missing imports, incorrect type hints, and consistent typos in the 'omitted' property across the codebase.