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>