feat(optimizer)!: type annotation for databricks REGR_SXX, REGR_SXY, REGR_SYY

[fivetran-amrutabhimsenayachit]

Summary

Adds Databricks type inference support for REGR_SXX (DOUBLE), REGR_SXY (DOUBLE), and REGR_SYY (DOUBLE), including a parser fix to handle the DISTINCT modifier correctly for these two-argument aggregates.

Tickets

• RD-1229643 (REGR_SXX) — DOUBLE, new typing + parser fix
• RD-1229644 (REGR_SXY) — DOUBLE, new typing + parser fix
• RD-1229645 (REGR_SYY) — DOUBLE, new typing + parser fix
• RD-1229647 (REPEAT) — already complete, no changes
• RD-1229648 (REPLACE) — already complete, no changes

Test plan

• make style — PASS
• make unit — PASS (1342 tests, 0 failures)
• test_annotate_funcs fixture — PASS
• Engine verified on Databricks: DISTINCT and OVER variants return DOUBLE

[github-actions]

SQLGlot Integration Test Results

✅ All tests passed

Comparing:

• this branch (sqlglot:type-inference-batch-4 @ sqlglot d0011b6)
• baseline (main @ sqlglot 122b44f)

Overall

main: 192416 total, 153532 passed (pass rate: 79.8%)

sqlglot:type-inference-batch-4: 180222 total, 142385 passed (pass rate: 79.0%)

Transitions:
No change

Dialect pair changes: 0 previous results not found, 3 current results not found

✅ All tests passed

[geooo109]

Let's refactor here:

    def _regr_sql(self, expression: exp.RegrAvgx  | exp.RegrSxx | exp.RegrSyy) -> str:
        name = expression.sql_name()
        x = expression.expression
        if isinstance(x, exp.Distinct):
            return self.func(name, exp.Distinct(expressions=[expression.this]), *x.expressions)
       
        return self.func(name, expression.this, x)

Then we can resue this ^ for all the 3 cases.