[red-knot] Add control flow support for match statement (#13241)

## Summary

This PR adds support for control flow for match statement.

It also adds the necessary infrastructure required for narrowing
constraints in case blocks and implements the logic for
`PatternMatchSingleton` which is either `None` / `True` / `False`. Even
after this the inferred type doesn't get simplified completely, there's
a TODO for that in the test code.

## Test Plan

Add test cases for control flow for (a) when there's a wildcard pattern
and (b) when there isn't. There's also a test case to verify the
narrowing logic.

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Co-authored-by: Carl Meyer <carl@astral.sh>

crates/red_knot_python_semantic/src/semantic_index.rs

@@ -21,6 +21,7 @@ use crate::Db;
 
 pub mod ast_ids;
 mod builder;
+pub(crate) mod constraint;
 pub mod definition;
 pub mod expression;
 pub mod symbol;