NCO-57: Initial implementation of async analytics

[davidkelly]

Add async query API:

• StartQueryAsync, FetchStatusAsync, FetchResultsAsync, DiscardResultsAsync, CancelQueryAsync with QueryHandle, QueryStatus, and StartQueryOptions
• Add QueryStatus state machine with AreResultsReady, IsError, and GetResults() including defensive handling of undocumented "failed" status observed from server
• Add comprehensive Debug-level logging across all sync and async methods with request-sent/response-received pairs including URIs, handles, request IDs, and HTTP status codes (events 1–18)
• Add log redaction framework ported from couchbase-net-client:
• Redact system data (URIs, handles, request IDs) and user data (query statements) in all log messages; default RedactionLevel.None preserves existing behavior
• Add ClusterOptions.WithRedactionLevel() for configuring redaction
• Add unit tests: QueryStatusTests ,RedactionTests

[jeffrymorris]

LGTM