Outer join elimination does not handle `IS TRUE` correctly

[neilconway]

Describe the bug

We don't handle nested IS TRUE clauses correctly when converting outer joins to inner joins.

To Reproduce

DataFusion CLI v53.1.0
> create table t1(a int, b int, c varchar);
create table t2(x int, y int, z varchar);

insert into t1 values (1, 10, 'a'), (2, 20, 'b'), (3, 30, 'c'), (null, 40, 'd');
insert into t2 values (1, 100, 'p'), (2, 200, 'q'), (null, 300, 'r');

0 row(s) fetched.
Elapsed 0.057 seconds.

0 row(s) fetched.
Elapsed 0.001 seconds.

+-------+
| count |
+-------+
| 4     |
+-------+
1 row(s) fetched.
Elapsed 0.042 seconds.

+-------+
| count |
+-------+
| 3     |
+-------+
1 row(s) fetched.
Elapsed 0.001 seconds.

> select * from t1 left join t2 on t1.a = t2.x where not ((t2.y > 150) is true);
+---+----+---+---+-----+---+
| a | b  | c | x | y   | z |
+---+----+---+---+-----+---+
| 1 | 10 | a | 1 | 100 | p |
+---+----+---+---+-----+---+
1 row(s) fetched.
Elapsed 0.028 seconds.

Expected behavior

DuckDB and Postgres produce the expected results:

create table t1(a int, b int, c varchar);
create table t2(x int, y int, z varchar);
insert into t1 values (1, 10, 'a'), (2, 20, 'b'), (3, 30, 'c'), (null, 40, 'd');
insert into t2 values (1, 100, 'p'), (2, 200, 'q'), (null, 300, 'r');
create table t2(x int, y int, z varchar);

insert into t1 values (1, 10, 'a'), (2, 20, 'b'), (3, 30, 'c'), (null, 40, 'd');
insert into t2 values (1, 100, 'p'), (2, 200, 'q'), (null, 300, 'r');

select * from t1 left join t2 on t1.a = t2.x where not ((t2.y > 150) is true);
┌───────┬───────┬─────────┬───────┬───────┬─────────┐
│   a   │   b   │    c    │   x   │   y   │    z    │
│ int32 │ int32 │ varchar │ int32 │ int32 │ varchar │
├───────┼───────┼─────────┼───────┼───────┼─────────┤
│     1 │    10 │ a       │     1 │   100 │ p       │
│     3 │    30 │ c       │  NULL │  NULL │ NULL    │
│  NULL │    40 │ d       │  NULL │  NULL │ NULL    │
└───────┴───────┴─────────┴───────┴───────┴─────────┘

Additional context

No response

[neilconway]

take