[slorello89]

Filtered vector queries on Search on Flex can require an explicit execution policy. This adds an optional hybrid_policy argument to the translator, sync/async executors, and executor factories.

• Accept ADHOC_BF and BATCHES, normalize case, and reject invalid values.
• Emit HYBRID_POLICY for filtered FT.SEARCH KNN queries.
• Emit FILTER ... POLICY for filtered FT.HYBRID queries, mapping ADHOC_BF to ADHOC.
• Preserve existing translation when no policy is supplied or no filter is present.
• Add API documentation, a usage example, and regression coverage.

Validation: all 629 tests passed; formatting, import sorting, and type checks passed. Both policies were also exercised through synchronous and asynchronous RedisVL SQL execution against Redis 8.4 and through the RAM/Flex compatibility runs.

Companion RedisVL API PR: redis/redis-vl-python#779