[MIRROR] Fixes SS13.register_signal throwing unclear errors when called on deleted datums (#27293)

* Cleans up the SS13_base lua file and adds a new lua file for easily handling multiple signals on different objects. (#82458)

## About The Pull Request
Cleaned up the SS13.register_signal and SS13.unregister_signal, removing
the weird list shifting.
Also adds a new lua file that can be included for the use of registering
different signals on various datums and being able to clear them all in
1 function.
Removed the make_easy_clear_function option when registering a signal
via lua because I don't think it's used by anyone and it lacks any sort
of versatility. Users can just create their own function for clearing
signals from a datum.

Also updates the documentation for HARDDELETES.md as
COMSIG_PARENT_QDELETING was renamed to COMSIG_QDELETING

## Why It's Good For The Game
New handler file makes registering signals in batches a lot easier if
you want to clear them in one go without clearing unrelated callbacks on
the same datum. The list shifting in SS13.register_signal had pretty
significant performance problems, so removing that will make registering
and unregistering signals faster.

## Changelog
🆑
admin: LUA - Adds a new library called handler_group. Include it in your
files by doing require('handler_group')
/🆑

---------

Co-authored-by: Watermelon914 <3052169-Watermelon914@users.noreply.gitlab.com>

* Fixes SS13.register_signal throwing unclear errors when called on deleted datums (#82597)

## About The Pull Request
See title

## Why It's Good For The Game
More descriptive error message

## Changelog
🆑
fix: LUA: Registering a signal on a deleted datum will throw a more
descriptive error message.
/🆑

---------

Co-authored-by: Watermelon914 <3052169-Watermelon914@users.noreply.gitlab.com>

---------

Co-authored-by: Watermelon914 <37270891+Watermelon914@users.noreply.github.com>
Co-authored-by: Watermelon914 <3052169-Watermelon914@users.noreply.gitlab.com>

lua/handler_group.lua

@@ -0,0 +1,49 @@
+local SS13 = require('SS13')
+local HandlerGroup = {}
+HandlerGroup.__index = HandlerGroup
+
+function HandlerGroup.new()
+	return setmetatable({
+		registered = {}
+	}, HandlerGroup)
+end
+
+-- Registers a signal on a datum for this handler group instance.
+function HandlerGroup:register_signal(datum, signal, func)
+	local callback = SS13.register_signal(datum, signal, func)
+	if not callback then
+		return
+	end
+	table.insert(self.registered, { datum = datum, signal = signal, callback = callback  })
+end
+
+-- Clears all the signals that have been registered on this HandlerGroup
+function HandlerGroup:clear()
+	for _, data in self.registered do
+		if not data.callback or not data.datum then
+			continue
+		end
+		SS13.unregister_signal(data.datum, data.signal, data.callback)
+	end
+	table.clear(self.registered)
+end
+
+-- Clears all the signals that have been registered on this HandlerGroup when a specific signal is sent on a datum.
+function HandlerGroup:clear_on(datum, signal, func)
+	SS13.register_signal(datum, signal, function(...)
+		if func then
+			func(...)
+		end
+		self:clear()
+	end)
+end
+
+-- Registers a signal on a datum and clears it after it is called once.
+function HandlerGroup.register_once(datum, signal, func)
+	local callback = HandlerGroup.new()
+	callback:clear_on(datum, signal, func)
+	return callback
+end
+
+
+return HandlerGroup