Refactor: Move compiler node definitions to src/ast/nodes

The `bound_nodes.rs` file has been removed and its contents have been
moved to `src/ast/nodes.rs`. This consolidates all AST node definitions
into a single module, improving organization and maintainability.

The `compiler` modules now import these definitions from
`crate::ast::nodes` instead of `crate::ast::compiler::bound_nodes`.

tests/error_recovery.rs

@@ -1,4 +1,4 @@
-use myc::ast::compiler::bound_nodes::TypedNode;
+use myc::ast::nodes::TypedNode;
 use myc::ast::environment::Environment;
 use myc::ast::types::StaticType;