Name the connection pool reaper thread

Naming threads can be helpful for debugging (e.g. getting an overview of
what's running with `Thread.list.map(&:name)` or `ps -T -p PID`.

We noticed our reaper didn't have a name, so this commit adds one.

We've intentionally kept the name short (< 15 characters), since there
are platform limitations on the length of the underlying thread name.

Co-authored-by: John Hawthorn <[email protected]>

Author: composerinteralia

activerecord/lib/active_record/connection_adapters/abstract/connection_pool/reaper.rb

@@ -43,6 +43,7 @@ def spawn_thread(frequency)
                 # Advise multi-threaded app servers to ignore this thread for
                 # the purposes of fork safety warnings
                 Thread.current.thread_variable_set(:fork_safe, true)
+                Thread.current.name = "AR Pool Reaper"
                 running = true
                 while running
                   sleep t