After the timer rewrite only the timer callbacks are executed
but stages are no longer automatically marked for execution. Timers that
send messages are not affected as that uses the standard activation mechanism.

This allows excluding those tests based on the pattern '^.*(?<!IT)$' in
IntelliJ

Unless we need to remove elements in the middle of a list, an array based variant is always faster.

There's no need for the current replica to further process the
request.

If a reply message completes a certificate while in the same
moment the lock acquire inside invoke times out then the following
retry instruction can reset the certificate even though the lock was
already released.