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/modular_computers/computers/item/computer.dm

@@ -393,7 +393,7 @@
 		if(3)
 			data["PC_ntneticon"] = "sig_lan.gif"
 
-	if(idle_threads.len)
+	if(length(idle_threads))
 		var/list/program_headers = list()
 		for(var/I in idle_threads)
 			var/datum/computer_file/program/P = I
@@ -486,7 +486,7 @@
 	return TRUE
 
 /obj/item/modular_computer/screwdriver_act(mob/user, obj/item/tool)
-	if(!all_components.len)
+	if(!length(all_components))
 		to_chat(user, span_warning("This device doesn't have any components installed."))
 		return
 	var/list/component_names = list()
@@ -494,9 +494,9 @@
 		var/obj/item/computer_hardware/H = all_components[h]
 		component_names.Add(H.name)
 
-	var/choice = input(user, "Which component do you want to uninstall?", "Computer maintenance", null) as null|anything in sort_list(component_names)
+	var/choice = tgui_input_list(user, "Component to uninstall", "Computer maintenance", sort_list(component_names))
 
-	if(!choice)
+	if(isnull(choice))
 		return
 
 	if(!Adjacent(user))
@@ -528,7 +528,7 @@
 			return
 
 	if(W.tool_behaviour == TOOL_WRENCH)
-		if(all_components.len)
+		if(length(all_components))
 			to_chat(user, span_warning("Remove all components from \the [src] before disassembling it."))
 			return
 		new /obj/item/stack/sheet/iron( get_turf(src.loc), steel_sheet_cost )