Implement HandleClusteredCreateAsync, HandleClusteredUpdateAsync, and
HandleClusteredDeleteAsync on StreamApiHandlers, and HandleClusteredCreateAsync
and HandleClusteredDeleteAsync on ConsumerApiHandlers. These handlers propose
operations to the meta RAFT group (JetStreamMetaGroup) instead of operating on
the local StreamManager/ConsumerManager, matching the Go jsClusteredStreamRequest
and jsClusteredConsumerRequest patterns (jetstream_cluster.go:7620-8265).
Ten tests in ClusteredApiTests.cs verify: stream create proposes to meta group,
duplicate-stream error, not-leader error (code 10003), stream update, stream
delete, not-found-on-delete, consumer create on stream, consumer-on-missing-stream
error, consumer delete, and not-found consumer delete.
Add ILeaderForwarder interface and DefaultLeaderForwarder, update
JetStreamApiRouter with RouteAsync + ForwardedCount so non-leader nodes
can attempt to forward mutating requests to the meta-group leader before
falling back to a NotLeader error response.
Stream lifecycle, publish/ack, consumer delivery, retention policy,
API endpoints, cluster formation, and leader failover tests ported
from Go nats-server reference. 1006 total tests passing.
