Refactor bound node types for clarity

Introduce generic `CompilerPhase` trait to unify different stages of the
bound AST. Rename `LocalSlot` to `VirtualId` and introduce `StackOffset`
for clearer distinction between compile-time and run-time addressing.
Update type aliases and implementations to reflect these changes.

src/ast/compiler/optimizer/inliner.rs

@@ -1,4 +1,4 @@
-use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind, LocalSlot};
+use crate::ast::compiler::bound_nodes::{Address, AnalyzedNode, BoundKind, VirtualId};
 use crate::ast::types::{Purity, Value};
 use crate::ast::vm::Closure;
 use std::cell::RefCell;
@@ -24,7 +24,7 @@ impl<'a> Inliner<'a> {
         }
     }
 
-    pub fn is_inlinable_value(&self, val: &Value, addr: Address) -> bool {
+    pub fn is_inlinable_value(&self, val: &Value, addr: Address<VirtualId>) -> bool {
         let type_ok = match val {
             Value::Int(_)
             | Value::Float(_)
@@ -141,7 +141,7 @@ impl<'a> Inliner<'a> {
         }
     }
 
-    pub fn collect_parameter_slots_set(&self, node: &AnalyzedNode, slots: &mut HashSet<LocalSlot>) {
+    pub fn collect_parameter_slots_set(&self, node: &AnalyzedNode, slots: &mut HashSet<VirtualId>) {
         match &node.kind {
             BoundKind::Define {
                 addr: Address::Local(slot),