Use standard SIGHUP and SIGTERM handlers in autoprewarm module

Hi,

Autoprewarm module is using it's own SIGHUP(apw_sigterm_handler,
got_sigterm) and SIGTERM(apw_sighup_handler, got_sighup) handlers which are
similar to standard signal handlers(except for a difference [1]). Isn't it
good to remove them and use standard SignalHandlerForConfigReload and
SignalHandlerForShutdownRequest?

Attaching the patch for the above changes.

Looks like the commit[2] replaced custom handlers with standard handlers.

Thoughts?

[1] apw_sigterm_handler() and apw_sighup_handler() use MyProc->procLatch
if (MyProc)
SetLatch(&MyProc->procLatch);
where as standard handlers use MyLatch
SetLatch(MyLatch);
Both MyProc->procLatch and MyLatch point to same, see comment from global.c
/*
* MyLatch points to the latch that should be used for signal handling by
the
* current process. It will either point to a process local latch if the
* current process does not have a PGPROC entry in that moment, or to
* PGPROC->procLatch if it has.
*Thus it can always be used in signal handlers, * without checking for its
existence.*
*/
struct Latch *MyLatch;

(gdb) p MyProc->procLatch
$6 = {is_set = 0, is_shared = true, owner_pid = 1448807}
(gdb) p MyLatch
*$7 = (struct Latch *) 0x7fcacc6d902c*
(gdb) p &MyProc->procLatch
*$8 = (Latch *) 0x7fcacc6d902c*
(gdb) p *MyLatch
$9 = {is_set = 0, is_shared = true, owner_pid = 1448807}

[2] commit 1e53fe0e70f610c34f4c9e770d108cd94151342c
Author: Robert Haas <rhaas(at)postgresql(dot)org>
Date: 2019-12-17 13:03:57 -0500

Use PostgresSigHupHandler in more places.

There seems to be no reason for every background process to have
its own flag indicating that a config-file reload is needed.
Instead, let's just use ConfigFilePending for that purpose
everywhere.

With Regards,
Bharath Rupireddy.
EnterpriseDB: http://www.enterprisedb.com