Discovery: node join requests should be handled at lower priority than master election

When a node is elected as master or receives a join request, we submit a cluster state update task. We should give the node join update task a lower priority than the elect as master to increase the chance it will not be rejected. During master election there is a big chance that these will happen concurrently.

This commit lowers the priority of node joins from IMMEDIATE to URGENT

Closes #7733
Bulk operation can create duplicates on primary relocation
When executing a bulk request, with create index operation and auto generate id, if while the primary is relocating the bulk is executed, and the relocation is done while N items from the bulk have executed, the full shard bulk request will be retried on the new primary. This can create duplicates because the request is not makred as potentially holding conflicts.

This change carries over the response for each item on the request level, and if a conflict is detected on the primary shard, and the response is there (indicating that the request was executed once already), use the mentioned response as the actual response for that bulk shard item.

On top of that, when a primary fails and is retried, the change now marks the request as potentially causing duplicates, so the actual impl will do the extra lookup needed.

This change also fixes a bug in our exception handling on the replica, where if a specific item failed, and its not an exception we can ignore, we should actually cause the shard to fail.

closes #7729
[SNAPSHOT] Trigger retry logic also if we hit a JsonException

We rely on retry logic when reading a snapshot since it's concurrently
serialized. We should move to a better logic here but the refactoring
of the blobstore change the semantics and this now throws Json
exceptions rather than returning an unexpected Token
[TEST] Improve HTTP support in TestClusters

This commit disalbes HTTP for all the suite and test scope tests
since it's an unused / unneeded module which takes time to startup.
This also uses a JVM private port range for HTTP ports to ensure
there are no cross JVM conflicts.