issue: #40532
- start timeticksync at rootcoord if the streaming service is not
available
- stop timeticksync if the streaming service is available
- open a read-only wal if some nodes in cluster is not upgrading to 2.6
- allow to open read-write wal after all nodes in cluster is upgrading
to 2.6
---------
Signed-off-by: chyezh <chyezh@outlook.com>
issue: #38399
- Embed the query node into streaming node to make delegator available
at streaming node.
- The embedded query node has a special server label
`QUERYNODE_STREAMING-EMBEDDED`.
- Change the balance strategy to make the channel assigned to streaming
node as much as possible.
Signed-off-by: chyezh <chyezh@outlook.com>
issue: #33285
- add two grpc resolver (by session and by streaming coord assignment
service)
- add one grpc balancer (by serverID and roundrobin)
- add lazy conn to avoid block by first service discovery
- add some utility function for streaming service
Signed-off-by: chyezh <chyezh@outlook.com>
