opt: internal error: inconsistent Case return types

[yuzefovich]

We have several reproductions for this internal error:

#125115

CREATE FUNCTION a() RETURNS RECORD LANGUAGE SQL AS $$ SELECT ('\x00'::BYTES,) $$;
CREATE FUNCTION b() RETURNS RECORD LANGUAGE SQL AS $$ SELECT B'00', 1 $$;
SELECT CASE WHEN false THEN a() ELSE b() END;

#130813

CREATE TABLE v00 (v01 STRING);
UPSERT INTO v00 ( v01 ) ( SELECT 'random_str' ) RETURNING CASE WHEN NULL THEN IFERROR ( NULL, 0 ) END;

#138890

CREATE TABLE t0 (c0 BOOL);
WITH temp_table(c0)  AS ((VALUES (NULL))) SELECT t0.c0 FROM t0 FULL OUTER MERGE JOIN temp_table ON false WHERE NULLIF((temp_table.c0) IN (true), (true));

Jira issue: CRDB-46409