[ty] Some more simplifications when rendering constraint sets (#21009)

This PR adds another useful simplification when rendering constraint
sets: `T = int` instead of `T = int ∧ T ≠ str`. (The "smaller"
constraint `T = int` implies the "larger" constraint `T ≠ str`.
Constraint set clauses are intersections, and if one constraint in a
clause implies another, we can throw away the "larger" constraint.)

While we're here, we also normalize the bounds of a constraint, so that
we equate e.g. `T ≤ int | str` with `T ≤ str | int`, and change the
ordering of BDD variables so that all constraints with the same typevar
are ordered adjacent to each other.

Lastly, we also add a new `display_graph` helper method that prints out
the full graph structure of a BDD.

---------

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

crates/ty_python_semantic/src/semantic_index/definition.rs

@@ -22,7 +22,12 @@ use crate::unpack::{Unpack, UnpackPosition};
 /// because a new scope gets inserted before the `Definition` or a new place is inserted
 /// before this `Definition`. However, the ID can be considered stable and it is okay to use
 /// `Definition` in cross-module` salsa queries or as a field on other salsa tracked structs.
+///
+/// # Ordering
+/// Ordering is based on the definition's salsa-assigned id and not on its values.
+/// The id may change between runs, or when the definition was garbage collected and recreated.
 #[salsa::tracked(debug, heap_size=ruff_memory_usage::heap_size)]
+#[derive(Ord, PartialOrd)]
 pub struct Definition<'db> {
     /// The file in which the definition occurs.
     pub file: File,