Client trace logs should include Cluster as key where appropriate

There are a few client trace logs that currently do not have the Cluster as an XML/log key indicating what cluster they are talking to, and I think that it would be useful to have that information to support applications where one client connects to multiple clusters. Some examples are:

1. `LargeTransaction`
2. `LargePacket` (which *does* contain peer information, but having the cluster as well can help aggregate requests)
3. `ConnectionRejected` (similar to `LargePacket`)

There are probably others, but the basic idea is that anything that is talking to a specific cluster or a specific FDB server on a specific cluster should probably include the Cluster as a logging key (which may be easier to plumb through in some circumstances than others).

Start by locating the client trace-log sites for LargeTransaction, LargePacket, and ConnectionRejected, then inspect how cluster context is available at each site. Check nearby logging tests or coverage if present. Done means logs that identify a specific cluster or server include Cluster wherever that context can be provided, with existing behavior preserved.

Written by the indexing model from the issue text.