TGUI list conversions + bug fixes (#63354)

About The Pull Request

    Converts more inputs to TGUI. Possibly all user-facing input lists in the game.
    Did any surrounding text/number inputs as well
    Added null choice support so users can press cancel.
    Added some misc TGUI input fixes
    Fixed custom vendors while I was there

I refactored a lot of code while just poking around.
Primarily, usage of .len in files where I was already working on lists.
Some code was just awful - look at guardian.dm and its non use of early returns
If there are any disputes, I can revert it just fine, those changes are not integral to the PR.
Why It's Good For The Game

Fixes #63629
Fixes #63307
Fixes custom vendors /again/
Text input is more performant.
Part of a long series of TGUI conversion to make the game more visually appealing
Changelog

cl
refactor: The majority of user facing input lists have been converted to TGUI.
refactor: Tgui text inputs now scale with entered input.
fix: Many inputs now properly accept cancelling out of the menu.
fix: Fixes an edge case where users could not press enter on number inputs.
fix: Custom vendor bluescreen.
fix: You can now press ENTER on text inputs without an entry to cancel.
/cl

code/modules/mob/dead/dead.dm

@@ -51,7 +51,7 @@ INITIALIZE_IMMEDIATE(/mob/dead)
 	. += "Players: [SSticker.totalPlayers]"
 	if(client.holder)
 		. += "Players Ready: [SSticker.totalPlayersReady]"
-		. += "Admins Ready: [SSticker.total_admins_ready] / [GLOB.admins.len]"
+		. += "Admins Ready: [SSticker.total_admins_ready] / [length(GLOB.admins)]"
 
 /mob/dead/proc/server_hop()
 	set category = "OOC"
@@ -62,7 +62,7 @@ INITIALIZE_IMMEDIATE(/mob/dead)
 	var/list/our_id = CONFIG_GET(string/cross_comms_name)
 	var/list/csa = CONFIG_GET(keyed_list/cross_server) - our_id
 	var/pick
-	switch(csa.len)
+	switch(length(csa))
 		if(0)
 			remove_verb(src, /mob/dead/proc/server_hop)
 			to_chat(src, span_notice("Server Hop has been disabled."))
@@ -71,7 +71,7 @@ INITIALIZE_IMMEDIATE(/mob/dead)
 		else
 			pick = tgui_input_list(src, "Server to jump to", "Server Hop", csa)
 
-	if(!pick)
+	if(isnull(pick))
 		return
 
 	var/addr = csa[pick]

code/modules/mob/dead/observer/observer.dm

@@ -118,7 +118,7 @@ GLOBAL_VAR_INIT(observer_default_invisibility, INVISIBILITY_OBSERVER)
 
 	if(!T || is_secret_level(T.z))
 		var/list/turfs = get_area_turfs(/area/shuttle/arrival)
-		if(turfs.len)
+		if(length(turfs))
 			T = pick(turfs)
 		else
 			T = SSmapping.get_station_center()
@@ -441,14 +441,17 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 			filtered += A
 	var/area/thearea = tgui_input_list(usr, "Area to jump to", "BOOYEA", filtered)
 
-	if(!thearea)
+	if(isnull(thearea))
+		return
+	if(!isobserver(usr))
+		to_chat(usr, span_warning("Not when you're not dead!"))
 		return
 
 	var/list/L = list()
 	for(var/turf/T in get_area_turfs(thearea.type))
 		L+=T
 
-	if(!L || !L.len)
+	if(!L || !length(L))
 		to_chat(usr, span_warning("No area available."))
 		return
 
@@ -510,8 +513,9 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 	var/target = null
 
 	target = tgui_input_list(usr, "Please, select a player!", "Jump to Mob", possible_destinations)
-
-	if (!target || !isobserver(usr))
+	if(isnull(target))
+		return
+	if (!isobserver(usr))
 		return
 
 	var/mob/destination_mob = possible_destinations[target] //Destination mob
@@ -879,8 +883,9 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 	var/target = null
 
 	target = tgui_input_list(usr, "Please, select a player!", "Jump to Mob", possible_destinations)
-
-	if (!target || !isobserver(usr))
+	if(isnull(target))
+		return
+	if (!isobserver(usr))
 		return
 
 	var/mob/chosen_target = possible_destinations[target]
@@ -1032,7 +1037,7 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 			I.appearance = MA
 			t_ray_images += I
 	stored_t_ray_images += t_ray_images
-	if(t_ray_images.len)
+	if(length(t_ray_images))
 		if(t_ray_view)
 			client.images += t_ray_images
 		else