Allow boolean Expr simplification even when nullable

[eejbyfeldt]

Which issue does this PR close?

Closes #12769.

Rationale for this change

The nullable requirement seem to have been added in #1401 but as far as
I can tell they are not needed for these 2 cases.

I think this can be shown using this truth table: (generated using
datafusion-cli without this patch)

> CREATE TABLE t (v BOOLEAN) as values (true), (false), (NULL);
> select t.v, t2.v, t.v AND (t.v OR t2.v), t.v OR (t.v AND t2.v) from t cross join t as t2;
+-------+-------+---------------------+---------------------+
| v     | v     | t.v AND t.v OR t2.v | t.v OR t.v AND t2.v |
+-------+-------+---------------------+---------------------+
| true  | true  | true                | true                |
| true  | false | true                | true                |
| true  |       | true                | true                |
| false | true  | false               | false               |
| false | false | false               | false               |
| false |       | false               | false               |
|       | true  |                     |                     |
|       | false |                     |                     |
|       |       |                     |                     |
+-------+-------+---------------------+---------------------+

And it seems Spark applies both of these and DuckDB applies only the
first one.

What changes are included in this PR?

Removes the not nullable guard and therefore allows some boolean simplification in more cases.

Are these changes tested?

Existing tests (some had to be modified).

Are there any user-facing changes?

No API changes. But user might notice that more expressions are simplified.

[eejbyfeldt]

These changes are neccessary to avoid us simplifiying these conditions and therefore changing what is gets tested here.

[alamb]

Thank you @eejbyfeldt -- this is an excellent find.

I went through this simplification several times in my head and I agree with your assessment that the nullability of B does not affect these particular rewrites

cc @Dandandan and @NGA-TRAN (perhaps you can triple check this logic, given how subtle it is)

[jayzhan211]

👍

[alamb]

🚀