[Feature] Add multi-flag fuzzy hash support with Lua-based Redis update path

[Feature] Add multi-flag fuzzy hash support with Lua-based Redis update path

Support up to 8 flag slots per fuzzy hash (primary + 7 extra), enabling
multiple rules to match against the same digest with independent flag/value
pairs. The highest-value flag is always promoted to the primary slot for
backward compatibility.

The Redis update path (ADD/DEL/REFRESH) is moved from a C MULTI/EXEC
pipeline with an embedded EVAL string to a proper Lua architecture
following the Bayes pattern: a Redis script in lualib/redis_scripts/
loaded via lua_redis.load_redis_script_from_file(), with a Lua module
(lua_fuzzy_redis.lua) providing an async update functor called from C
via lua_pcall. This gives automatic EVALSHA + NOSCRIPT recovery and
keeps the multi-flag merge logic in a maintainable .lua file.

Wire protocol extended with epoch 12 (RSPAMD_FUZZY_EPOCH12) carrying
rspamd_fuzzy_reply_v2 with n_extra_flags and up to 7 extra flag entries.