…stic#53873)

This commit changes the pre_filter_shard_size default from 128 to unspecified.
This allows to apply heuristics based on the request and the target indices when deciding
whether the can match phase should run or not. When unspecified, this pr runs the can match phase
automatically if one of these conditions is met:
  * The request targets more than 128 shards.
  * The request contains read-only indices.
  * The primary sort of the query targets an indexed field.
Users can opt-out from this behavior by setting the `pre_filter_shard_size` to a static value.

Closes elastic#39835