#3043)

* Filter out 'temporary placeholder' clsuter nodes with handshake flag that redis creates internally during cluster handshake (during initial cluster MEET, cluster MEET, cluster PONG sequence) since they are not expected to be usable members of the cluster at that time.

* - move the "ignore handshake nodes" logic deeper into the client, so external callers can still fetch the value
- add new IgnoreFromClient internal member for ^^^, and use
- support "handshake" etc in the in-proc test server
- support "only initially connect to default node" in the in-proc test server
- add a unit test that handshake nodes are ignored

* prove that ClusterNodesAsync still reports the node

* split out the two "handshake" test parts

* in-proc test server; make DefaultEndPoint reliable

* release notes

* put IsHandshake onto public API

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Co-authored-by: Marc Gravell <[email protected]>

* - propose new API to resolve product variant; only handles Redis, Valkey and Garnet at the moment

* - change the test-server to support multi-DB operations
- update the client to use the product-variant info to allow multi-DB operations on Valkey
- unit test with the toy-server

* naming is hard

* release notes

* Implement GRCA (redis/redis#14826)

* Flag [SER006]; remove [SER001]

* release notes

* Update ReleaseNotes.md