feat(hoist): pre-compute loop hoisting metadata at compilation time (#483)

Introduce a compiler pass that analyzes and pre-computes loop hoisting information
during policy compilation. This hoisted metadata is stored in lookup tables and made
available to downstream consumers:

- interpreter: use HoistedLoop entries during evaluation (replaces runtime scanning)
- type inference: can leverage pre-computed loop structure for type propagation
- RVM compiler: will consume hoisting metadata for optimized bytecode generation

Changes:
- populate loop hoisting tables during engine preparation and query snippet execution
- refactor eval_stmts_in_loop and eval_output_expr_in_loop to consume HoistedLoop directly
- add helper methods for accessing loop expressions, collections, and indices from HoistedLoop
- extend Lookup with get_checked and into_slots for safe query context access and merging

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

src/target/tests/deserialize.rs

@@ -268,8 +268,7 @@ fn test_target_deserialization_with_registry_schemas() {
 
     // We expect this to fail with a "not found in registry" error since we haven't
     // populated the registries with test data
-    if result.is_err() {
-        let error = result.unwrap_err();
+    if let Err(error) = result {
         assert!(matches!(
             error,
             TargetError::JsonParseError(_) | TargetError::DeserializationError(_)