Index client should use requestDeadline one avilable

Indexer setting queryport.client.readDeadline is same for all queries no control on user.

If requestDealine is present one should honor that

https://github.com/couchbase/query/blob/master/datastore/index.go#L834C30-L834C44

It is also better to ensure that actual TCP readDeadline is never less than index scan timeout setting value.