sql: allow anonymous args and numeric arg references in UDFs

[mgartner]

It is now possible to create UDFs with anonymous arguments that can be
referenced like a placeholder in a prepared statement. For example:

CREATE FUNCTION add(INT, INT) RETURNS INT LANGUAGE SQL AS $$
  SELECT $1 + $2;
$$

Named arguments can also be referenced by numeric placeholders. For
example:

CREATE FUNCTION add(x INT, y INT) RETURNS INT LANGUAGE SQL AS $$
  SELECT x + $2;
$$

Release note: None

Release justification: Adds critical functionality to a new feature.

[cockroach-teamcity]

This change is 

[mgartner]

All commits except for the last are from #85786. I'll rebase this PR when that one is merged.

[DrewKimball]

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @mgartner, @michae2, and @msirek)

---

pkg/sql/opt/optbuilder/create_function.go line 98 at r5 (raw file):

	// named arguments to the scope so that references to them in the body can
	// be resolved.
	// TODO(mgartner): Support numeric argument references, like $1. We should

[nit] this comment is outdated

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pkg/sql/opt/optbuilder/scalar.go line 628 at r5 (raw file):

	// can be resolved.
	//
	// TODO(mgartner): Support anonymous arguments and placeholder-like syntax

[nit] ditto

[mgartner]

TFTR!

Reviewable status: complete! 0 of 0 LGTMs obtained (and 1 stale) (waiting on @DrewKimball, @michae2, and @msirek)

---

pkg/sql/opt/optbuilder/create_function.go line 98 at r5 (raw file):

Previously, DrewKimball (Drew Kimball) wrote…

[nit] this comment is outdated

Good catch. Done.

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pkg/sql/opt/optbuilder/scalar.go line 628 at r5 (raw file):

Previously, DrewKimball (Drew Kimball) wrote…

[nit] ditto

Done.

[msirek]

Reviewed 3 of 7 files at r5, 16 of 16 files at r6, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (and 1 stale) (waiting on @DrewKimball and @michae2)

[mgartner]

This is going to be difficult to merge until we move the execution subtest section to the end of the udf test file: #86383.

[mgartner]

bors r+

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)