conlang: PATTERN MATCHING AND DESTRUCTURED BINDINGS WOOOOO

- Integrate the Match and Pattern nodes into the AST
  - TODO: `let x: T` is ambiguous with `let x: {}`. Currently the latter takes precedence in the parser.

- Implement pattern matching through unification in the interpreter.
  - It's not fast, but it works!

- Refactor destructuring assignments to use the new pattern functionality

compiler/cl-repl/examples/yaml.rs

@@ -380,6 +380,7 @@ pub mod yamlify {
             match self {
                 ExprKind::Quote(k) => k.yaml(y),
                 ExprKind::Let(k) => k.yaml(y),
+                ExprKind::Match(k) => k.yaml(y),
                 ExprKind::Assign(k) => k.yaml(y),
                 ExprKind::Modify(k) => k.yaml(y),
                 ExprKind::Binary(k) => k.yaml(y),