Adds Custom Announcement Dividers (#79071)

This ports a whole bunch of various PRs and commits from
https://github.com/effigy-se/effigy-se , with heavy refactoring to keep
it fresh for /tg/'s code standards.

## About The Pull Request

The whole slew of announcement touchups lately (as in #78995
(37db1ecbf8) / #79052
(12308dbd3d)) have made me realize how
much this stuff sucks. The author of these new spans was advertising
these in coding general, so I sat down and coded it. Look at the spans,
they're much nicer than what we had going on:

(ignore the capitalized alert status names, this was removed)

<details>
<summary>Dark Mode</summary>


![image](https://github.com/tgstation/tgstation/assets/34697715/107b8efb-b7a1-41ff-9d16-358c4dc3738d)

![image](https://github.com/tgstation/tgstation/assets/34697715/9e730dfe-7ba3-4edd-96bb-0630fe5e85cf)
</details>

<details>
<summary>Light Mode</summary>


![image](https://github.com/tgstation/tgstation/assets/34697715/57f642f9-ee17-4b16-8027-00a9350e9059)

![image](https://github.com/tgstation/tgstation/assets/34697715/b28b7f49-fd4f-420a-9313-e16b9781c07c)
</details>

This PR also features

* Major announcement code handling cleanup and refactor! There was a lot
of copypasta so let's distill it all down into one proc
* Better cacheing! We were doing a shit load of new string generation
needlessly! That's fixed now.
* Better string concatenation! Lists are better for string tree reasons.
It still works just as well, as you can see from the screenshots above.
Best of all, no fucking `<br>` dogshit everywhere!
* We don't use string equivalency in order to figure out the "type" of
an announcement. It's all defines now. This was a bonus that I just
coded in since it irritated me.
* Minor spellcheck of "announcement".
* All of our HTML string mangling stuff is now all span macros! I love
macros.

## Why It's Good For The Game

In the same vein of adding examine blocks (#67937
(b864589522)) because old examinations
tended to blend in with the chat and everything chat-wise used to suck
really hard- I think this is a really nice way to draw attention to
announcements in the chat box without needing a shit load of line breaks
that just really look ugly and have no real consistency. You can look at
the PRs/commits I linked above for an idea of just how ugly it could be
getting.

I haven't audited every announcement in this PR, we can tweak this down
the line.

## Changelog

🆑 LT3, san7890
add: Announcements have gotten a fresh coat of paint! They should be
popping with splendid new colors and should have a lot less ugly
linebreaks, while still managing to keep your attention at the screen.
/🆑

I know we didn't need to port all the CSS themes but I added them
anyways in case admins wanna have some fun.
There can probably be more code improvements, just figured I'd crack it
out while I had time.
The colors also seem fine, let me know if we need more redness or
something. It's okay for stuff to be toned down a bit imo, but that
should be done after a hot second.

---------

Co-authored-by: lessthanthree <83487515+lessthnthree@users.noreply.github.com>

code/controllers/subsystem/security_level.dm

@@ -39,7 +39,7 @@ SUBSYSTEM_DEF(security_level)
 	if(!selected_level)
 		CRASH("set_level was called with an invalid security level([new_level])")
 
-	announce_security_level(selected_level) // We want to announce BEFORE updating to the new level
+	level_announce(selected_level, current_security_level.number_level) // We want to announce BEFORE updating to the new level
 
 	SSsecurity_level.current_security_level = selected_level
 
@@ -56,18 +56,6 @@ SUBSYSTEM_DEF(security_level)
 	SSnightshift.check_nightshift()
 	SSblackbox.record_feedback("tally", "security_level_changes", 1, selected_level.name)
 
-/**
- * Handles announcements of the newly set security level
- *
- * Arguments:
- * * selected_level - The new security level that has been set
- */
-/datum/controller/subsystem/security_level/proc/announce_security_level(datum/security_level/selected_level)
-	if(selected_level.number_level > current_security_level.number_level) // We are elevating to this level.
-		minor_announce(selected_level.elevating_to_announcemnt, "Attention! Security level elevated to [selected_level.name]:", sound_override = selected_level.sound)
-	else // Going down
-		minor_announce(selected_level.lowering_to_announcement, "Attention! Security level lowered to [selected_level.name]:", sound_override = selected_level.sound)
-
 /**
  * Returns the current security level as a number
  */