[Feature] Unified hyperscan cache format for multipattern

[Feature] Unified hyperscan cache format for multipattern

Add C helper functions for serializing/deserializing hyperscan databases
with the unified format (magic, platform, CRC). Migrate multipattern from
raw .hsmp files to the unified .hs format compatible with re_cache.

- Add rspamd_hyperscan_serialize_with_header() and load_from_header()
- Update multipattern to use unified format with platform validation
- Fix CRC calculation in Lua bindings to match re_cache format