opt: extra filters add to lookup join ON condition when derive FK equalities

[mgartner]

In #90599 and 0cd8b49, we added equality conditions derived from FK constraints and uniqueness constraints. These equality conditions are unnecessarily added to the lookup join ON conditions in some cases. For example:

exec-ddl
CREATE TABLE p (
  r INT,
  id INT,
  PRIMARY KEY (r, id),
  UNIQUE WITHOUT INDEX (id)
)
----

exec-ddl
CREATE TABLE c (
  r INT,
  p_id INT,
  id INT,
  PRIMARY KEY (r, p_id, id),
  UNIQUE INDEX c_p_id_id_key (p_id, id),
  FOREIGN KEY (r, p_id) REFERENCES p (r, id)
)
----

opt
SELECT *
FROM p LEFT LOOKUP JOIN c@c_p_id_id_key
ON c.p_id = p.id AND c.id = 1234
----
left-join (lookup c@c_p_id_id_key)
 ├── columns: r:1(int!null) id:2(int!null) r:5(int) p_id:6(int) id:7(int)
 ├── flags: force lookup join (into right side)
 ├── key columns: [2 10] = [6 7]
 ├── lookup columns are key
 ├── stats: [rows=1000, distinct(6)=9.56179, null(6)=990]
 ├── key: (2)
 ├── fd: (2)-->(1,5-7), (6)-->(5)
 ├── project
 │    ├── columns: "lookup_join_const_col_@7":10(int!null) p.r:1(int!null) p.id:2(int!null)
 │    ├── stats: [rows=1000, distinct(1)=100, null(1)=0, distinct(2)=1000, null(2)=0, distinct(10)=1, null(10)=0]
 │    ├── key: (2)
 │    ├── fd: ()-->(10), (2)-->(1)
 │    ├── scan p
 │    │    ├── columns: p.r:1(int!null) p.id:2(int!null)
 │    │    ├── stats: [rows=1000, distinct(1)=100, null(1)=0, distinct(2)=1000, null(2)=0]
 │    │    ├── key: (2)
 │    │    └── fd: (2)-->(1)
 │    └── projections
 │         └── 1234 [as="lookup_join_const_col_@7":10, type=int]
 └── filters
      └── c.r:5 = p.r:1 [type=bool, outer=(1,5), constraints=(/1: (/NULL - ]; /5: (/NULL - ]), fd=(1)==(5), (5)==(1)]

Notice the synthesized filters at the bottom, c.r:5 = p.r:1, which are unnecessary.

Jira issue: CRDB-27156