Group shard request per node in the can match phase

[jimczi]

The can match phase fans out the original search request to all shards.
These individual requests have a cost:

• They serialize the same request multiple times.
• They need to resolve the index permissions multiple times.

Additionally, the broadcasting of these shard request is done on the network thread without any throttling, so search requests that target a large number of shards can disturb the cluster coordination, leading to nodes leaving the cluster.

Similar to #74648, we should move to a per-node request model for this phase. We can group shard request per node and perform the local operations for multiple shard/index at once. That would reduce the cost of coordination drastically and would leave room on data nodes to perform the operations on a separate thread pool.

[elasticmachine]

Pinging @elastic/es-search (Team:Search)

[jimczi]

Implemented in #79344