treewide: fix bash exit handlers

Transform exit handlers of the form
trap cleanup EXIT [INT] [TERM] [QUIT] [HUP] [ERR]
  (where cleanup is idempotent)
to
trap cleanup EXIT

This fixes a common bash antipattern.

Each of the above signals causes the script to exit. For each signal,
bash first handles the signal by running `cleanup` and then runs
`cleanup` again when handling EXIT.
(Exception:  `vscode/*` prevents the second run of `cleanup` by removing
the trap in cleanup`).

Simplify the cleanup logic by just trapping exit, which is always run
when the script exits due to any of the above signals.

Note: In case of borgbackup, the exit handler is not idempotent, but just
trapping EXIT guarantees that it's only run once.

maintainers/scripts/rebuild-amount.sh

@@ -35,7 +35,7 @@ toRemove=()
 cleanup() {
     rm -rf "${toRemove[@]}"
 }
-trap cleanup EXIT SIGINT SIGQUIT ERR
+trap cleanup EXIT
 
 MKTEMP='mktemp --tmpdir nix-rebuild-amount-XXXXXXXX'