opt: unnecessary cross-joins with when generating a lookup join with a lookup expression

[mgartner]

Notice in the query plan below that the cross-join to produce the lookup_join_const_col_@7 column is unnecessary.

exec-ddl
CREATE TABLE t1234 (
  a INT,
  b INT,
  c INT,
  INDEX (a, b, c)
)
----

opt expect=GenerateLookupJoinsWithFilter
SELECT m FROM small JOIN t1234 ON b IN (1, 2, 3) AND c > 0 AND m = a
----
project
 ├── columns: m:1!null
 └── inner-join (lookup t1234@t1234_a_b_c_idx)
      ├── columns: m:1!null a:6!null b:7!null c:8!null
      ├── lookup expression
      │    └── filters
      │         ├── m:1 = a:6 [outer=(1,6), constraints=(/1: (/NULL - ]; /6: (/NULL - ]), fd=(1)==(6), (6)==(1)]
      │         ├── b:7 IN (1, 2, 3) [outer=(7), constraints=(/7: [/1 - /1] [/2 - /2] [/3 - /3]; tight)]
      │         └── c:8 > 0 [outer=(8), constraints=(/8: [/1 - ]; tight)]
      ├── fd: (1)==(6), (6)==(1)
      ├── inner-join (cross)
      │    ├── columns: m:1 "lookup_join_const_col_@7":12!null
      │    ├── multiplicity: left-rows(one-or-more), right-rows(zero-or-more)
      │    ├── scan small
      │    │    └── columns: m:1
      │    ├── values
      │    │    ├── columns: "lookup_join_const_col_@7":12!null
      │    │    ├── cardinality: [3 - 3]
      │    │    ├── (1,)
      │    │    ├── (2,)
      │    │    └── (3,)
      │    └── filters (true)
      └── filters (true)

Jira issue: CRDB-14777

[mgartner]

This can cause incorrect query results:

statement ok
CREATE TABLE t79384a (
  k INT NOT NULL
)

statement ok
CREATE TABLE t79384b (
  a INT,
  b INT,
  c INT,
  INDEX (a, b, c)
)

statement ok
INSERT INTO t79384a VALUES (1)

statement ok
INSERT INTO t79384b VALUES (1, 1, 1)

# Tables t1 and t2 have a single row each, so this should never return more than
# one row.
query I
SELECT k FROM t79384a INNER LOOKUP JOIN t79384b ON k = a AND b IN (1, 2, 3) AND c > 0
----
1
1
1