Attached is a patch to eliminate unnecessary checks for matching 
clients/frames in `server-handle-delete-frame' and 
`server-kill-emacs-query-function'.

Previously, `server-handle-delete-frame' would iterate over all frames 
to check if there were any other frames associated with the current 
client. Now, it uses `seq-some' to stop iterating once it finds the 
first such frame.

Similarly, `server-kill-emacs-query-function' used to iterate over all 
clients, and then all buffers for *each* client to check if there were 
any live buffers associated with any clients. Now, it uses a pair of 
calls to `seq-some' to stop iterating once it finds a live buffer from 
any client.

I haven't benchmarked these changes since I hope the strategy of 
stopping iteration as soon as we can is uncontroversial. However, if you 
think it's important, I can try to generate some benchmarks.