Replace the single LState + coroutine model with an LState pool to
eliminate concurrent map read/write issues in gopher-lua. Each request
now gets a completely independent LState with its own Global table.
Key changes:
- Add LStatePool for managing pooled LState instances
- Remove shared Engine.L and coroutine-based execution
- Simplify coroutine.go: remove yield handling, use direct PCall
- Remove ngxRegisterMu lock (no longer needed with isolated LStates)
- Update config.go: add LStatePoolInitialSize/MaxSize settings
- Update tests to work with the new architecture
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
