Add gRPC supports for Search foundation; match-all query

[dayana-j]

Description

This PR adds gRPC support for Search for the opensearch-java client, starting with the match_all query type. It follows the same architecture pattern used for the Bulk gRPC transport.

The SearchRequestConverter converts the opensearch-java SearchRequest to the protobuf SearchRequest used by the gRPC SearchService. Currently only match_all is implemented:

private static org.opensearch.protobufs.MatchAllQuery convertMatchAll(MatchAllQuery matchAll) {
    org.opensearch.protobufs.MatchAllQuery.Builder builder =
        org.opensearch.protobufs.MatchAllQuery.newBuilder();
    if (matchAll.boost() != null) {
        builder.setBoost(matchAll.boost().floatValue());
    }
    return builder.build();
}

Other query types supported by the server (term, match, bool, range, k-NN, etc.) are not yet supported in this version and will throw an UnsupportedOperationException directing users to REST:

throw new UnsupportedOperationException(
     "Query type '" + query._kind() + "' is not yet supported for gRPC transport in this version. "
         + "Use REST transport for this query type."
 );

The SearchResponseConverter converts the protobuf SearchResponse back to the opensearch-java SearchResponse. This includes full response metadata (took, timed_out, _shards), hits metadata (total, max_score), and per-hit fields. Document _source is deserialized from raw bytes to the user's target class via the JsonpMapper:

static <TDocument> TDocument deserializeSource(
    byte[] sourceBytes, JsonpMapper jsonpMapper, Class<TDocument> tDocumentClass
) {
    InputStream stream = new ByteArrayInputStream(sourceBytes);
    jakarta.json.stream.JsonParser parser = jsonpMapper.jsonProvider().createParser(stream);
    parser.next();
    return jsonpMapper.deserialize(parser, tDocumentClass);
}

Additionally, the endpoint support was enhanced with a request-aware check (GrpcTransport.isEndpointSupported(endpoint, request)) as suggested by maintainer feedback. The HybridTransport now inspects the request content before routing: unsupported query types (term, match, bool, etc.) are automatically routed to REST instead of throwing an error, while match_all queries go over gRPC.

// match_all → routed to gRPC
 client.search(s -> s.index("idx").query(q -> q.matchAll(m -> m)), Doc.class);

 // term query → routed to REST automatically
 client.search(s -> s.index("idx").query(q -> q.term(t -> t.field("status").value("active"))), Doc.class);

Unit tests cover the request conversion for match_all with various parameters, verify that unsupported query types are correctly identified by the request-aware routing, and confirm proper routing behavior. Integration tests index documents via gRPC bulk, then search with match_all over gRPC and verify the full response.

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[dayana-j]

Thanks @reta