rgw/lua: add configurable runtime limit for the lua state

rgw/lua: add configurable runtime limit for the lua state

These changes improve the robustness and reliability of Lua script execution in the RADOS Gateway by enforcing configurable limit on execution time.

- Enhanced `lua_state_guard` to support configurable runtime limits for Lua scripts.
- Updated rgw.yaml.in to include new configuration options for Lua runtime limits.
- Added tests in `test_rgw_lua.cc` to verify Lua script execution with different runtime constraints.
- Updated Lua scripting documentation to reflect the new runtime limit configuration.

Signed-off-by: Oshry Avraham <oshryabiz@gmail.com>