Add support for warnings in FT.SEARCH, AGGREGATE and HYBRID

[uglide]

Note

Medium Risk
Changes public search result shapes and RESP3 reply parsing; incorrect parsing could hide or misreport timeout/partial-result warnings, though behavior is additive (empty warnings when absent).

Overview
Adds public Warnings on SearchResult, AggregationResult, and HybridSearchResult so callers can see RediSearch server messages (e.g. query timeout under the return / return-strict on-timeout policy). RESP3 FT.SEARCH and FT.AGGREGATE replies are parsed via a new ResponseParser.ParseWarnings helper that reads the top-level "warning" map field; FT.HYBRID warning parsing is enabled and exposed (works on RESP2 and RESP3).

Adds AggregationRequest.AddScores() to send the ADDSCORES option and surface @__score in the aggregation pipeline.

Integration tests cover search-on-timeout (fail throws RedisServerException; return yields partial results with timeout text in Warnings) for FT.SEARCH, FT.AGGREGATE, and FT.HYBRID (Redis ≥ 8.9). Shared test helpers: AssertIndexSize and SetSearchOnTimeout for cluster-wide config.

^{Reviewed by Cursor Bugbot for commit 7550da6. Bugbot is set up for automated code reviews on this repo. Configure here.}

[mgravell]

LGTM, but I'm wary of the list allocs that happen on the happy (no warnings to report) path