builtins: implement regr_avgy

[mneverov]

builtins: implement regr_avgy

Fixes: #41274

Release note (sql change): implement regr_avgy aggregation function.

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[yuzefovich]

Thanks!

nit: you could adjust the PR description (or the commit message) from See #41274 to something like Fixes: #41274 so that when the PR merges, the issue is closed automatically since regr_avgy is the last aggregate in that issue.

Thanks a lot for your work!

Reviewed 14 of 14 files at r1.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @mneverov)

---

pkg/sql/opt/operator.go, line 324 at r1 (raw file):

		VarPopOp, CovarPopOp, CovarSampOp, RegressionAvgXOp, RegressionInterceptOp,
		RegressionR2Op, RegressionSlopeOp, RegressionSXXOp, RegressionSXYOp,
		RegressionSYYOp, RegressionCountOp, RegressionAvgYOp:

super nit: it'd be nice to have AvgY and AvgX right next to each other.

[mneverov]

Hi @yuzefovich , thanks for the amazing support and patience :)!

Reviewable status: complete! 0 of 0 LGTMs obtained (and 1 stale) (waiting on @mneverov and @yuzefovich)

[yuzefovich]

bors r=yuzefovich

Reviewed 3 of 3 files at r2.
Reviewable status: complete! 0 of 0 LGTMs obtained (and 1 stale)

[craig]

Build succeeded:

• GitHub CI (Cockroach)