sql/schemachanger: missing function dep when adding an unvalidated constraint

[spilchen]

When altering a table to add a constraint that references a function, we fail to correctly establish the function dependency, resulting in an internal error. This only happens if the constraint is created as 'NOT VALID'. Validated constraints have the proper dependency tracking.

Reproduction

> CREATE TABLE IF NOT EXISTS t
(
    a TEXT
);
CREATE TABLE

> CREATE OR REPLACE FUNCTION func(a text) RETURNS boolean AS $$
BEGIN
  RETURN TRUE;
END;
$$ LANGUAGE plpgsql;
CREATE FUNCTION

> ALTER TABLE t
ADD CONSTRAINT IF NOT EXISTS check_a CHECK (func(a)) NOT VALID;
ERROR: internal error: executing declarative schema change StatementPhase stage 1 of 1 with 3 MutationType ops (rollback=false) for ALTER TABLE: error executing StatementPhase stage 1 of 1 with 3 MutationType ops: relation "t" (112): depends-on function "func" (113) has no corresponding depended-on-by back reference
SQLSTATE: XX000

https://github.com/cockroachlabs/support/issues/3458

Jira issue: CRDB-55424

Epic CRDB-55074

[blathers-crl]

Hi @spilchen, please add a branch-* label to identify the earliest affected branch for this C-bug

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