[Feature] Route all hyperscan cache operations through Lua backend

[Feature] Route all hyperscan cache operations through Lua backend

- Route file backend through Lua for consistency with redis/http
- Add zstd compression support with magic byte detection for backward
  compatibility (reads both .hs and .hs.zst files)
- Fix rspamd_util.stat() return value handling (returns err, stat tuple)
- Fix timer management for synchronous Lua callbacks to prevent early
  termination of re_cache compilation
- Fix use-after-free in load path by pre-counting pending items
- Add priority queue for re_cache compilation (short lists first)
- Add ev_run() flush before blocking hyperscan compilations to ensure
  busy notifications are sent
- Add hyperscan_notice_known() and hyperscan_get_platform_id() Lua APIs