[red-knot] Ensure differently ordered unions and intersections are understood as equivalent even inside arbitrarily nested tuples (#15740)

## Summary

On `main`, red-knot:
- Considers `P | Q` equivalent to `Q | P`
- Considered `tuple[P | Q]` equivalent to `tuple[Q | P]`
- Considers `tuple[P | tuple[P | Q]]` equivalent to `tuple[tuple[Q | P]
| P]`
- ‼️ Does _not_ consider `tuple[tuple[P | Q]]` equivalent to
`tuple[tuple[Q | P]]`

The key difference for the last one of these is that the union appears
inside a tuple that is directly nested inside another tuple.

This PR fixes this so that differently ordered unions are considered
equivalent even when they appear inside arbitrarily nested tuple types.

## Test Plan

- Added mdtests that fails on `main`
- Checked that all property tests continue to pass with this PR

crates/red_knot_python_semantic/resources/mdtest/type_properties/is_equivalent_to.md

@@ -84,4 +84,26 @@ static_assert(
 )
 ```
 
+## Unions containing tuples containing tuples containing unions (etc.)
+
+```py
+from knot_extensions import is_equivalent_to, static_assert, Intersection
+
+class P: ...
+class Q: ...
+
+static_assert(
+    is_equivalent_to(
+        tuple[tuple[tuple[P | Q]]] | P,
+        tuple[tuple[tuple[Q | P]]] | P,
+    )
+)
+static_assert(
+    is_equivalent_to(
+        tuple[tuple[tuple[tuple[tuple[Intersection[P, Q]]]]]],
+        tuple[tuple[tuple[tuple[tuple[Intersection[Q, P]]]]]],
+    )
+)
+```
+
 [the equivalence relation]: https://typing.readthedocs.io/en/latest/spec/glossary.html#term-equivalent