sql: use memo metadata to add UDFs to statement bundle

[mgartner]

We currently add UDFs to a statement bundle's schema.sql file with string matching:

cockroach/pkg/sql/explain_bundle.go

Line 832 in dea1354

// TODO: consider getting the udf sql body statements from the memo metadata.

Instead, we should use the metadata in the memo to determine which UDFs are relevant to the query.

As an added bonus, it would be great to ensure that UDFs referenced in table expressions are included in statement bundles. For example:

CREATE FUNCTION add_one(x INT) RETURNS INT IMMUTABLE LANGUAGE SQL AS 'SELECT x + 1';

CREATE TABLE t (
  a INT,
  b INT AS (add_one(a)) STORED
);

EXPLAIN ANALYZE (DEBUG) SELECT * FROM t;

The add_one UDF should be included in the statement bundle.

Jira issue: CRDB-28808

[michae2]

Might be done?

[blathers-crl]

Based on the specified backports for linked PR #132147, I applied the following new label(s) to this issue: branch-release-23.2, branch-release-24.1, branch-release-24.2. Please adjust the labels as needed to match the branches actually affected by this issue, including adding any known older branches.

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