Lua interpreter performance optimization (hot paths)

* The interpreter wasted cycles on unnecessary async/Promise wrapping
  and redundant allocations even for synchronous operations.
* Now: more "sync-first" evaluation — try the fast synchronous path
  first, only fall back to Promises when actually needed.
* In addition: fast paths for table access, variable lookups, string
  concat, arithmetic, and function calls; loops can re-enter sync mode
  after an async iteration resolves.
* Added benchmarks

Results: 1.3x–1.7x speedup across typical workloads (API calls, table
traversal, string ops), up to 1.92x in some cases.

Author: zefhemel