Pre-initialize global rayon threadpool (#41226)

We only use it a handful of times and the default amount of threads
(logical cpu core number) its spawns is overkill for this. This also
gives the threads names oppose to being labeled `<unknown>`

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/remote_server/Cargo.toml

@@ -65,6 +65,7 @@ util.workspace = true
 watch.workspace = true
 worktree.workspace = true
 thiserror.workspace = true
+rayon.workspace = true
 
 [target.'cfg(not(windows))'.dependencies]
 crashes.workspace = true