Bools and returns super-pr (#53221)

Replaces like 70-80% of 0 and such, as a side effect cleaned up a bunch of returns
Edit: Most left out ones are in mecha which should be done in mecha refactor already
Oh my look how clean it is

Co-authored-by: TiviPlus <TiviPlus>
Co-authored-by: Couls <coul422@gmail.com>

code/modules/mob/dead/new_player/login.dm

@@ -6,7 +6,7 @@
 		client.set_db_player_flags()
 	if(!mind)
 		mind = new /datum/mind(key)
-		mind.active = 1
+		mind.active = TRUE
 		mind.current = src
 
 	. = ..()

code/modules/mob/dead/new_player/new_player.dm

@@ -108,10 +108,10 @@
 
 /mob/dead/new_player/Topic(href, href_list[])
 	if(src != usr)
-		return 0
+		return
 
 	if(!client)
-		return 0
+		return
 
 	//Determines Relevent Population Cap
 	var/relevant_cap
@@ -124,7 +124,7 @@
 
 	if(href_list["show_preferences"])
 		client.prefs.ShowChoices(src)
-		return 1
+		return TRUE
 
 	if(href_list["ready"])
 		var/tready = text2num(href_list["ready"])
@@ -451,7 +451,7 @@
 	if(mind)
 		if(transfer_after)
 			mind.late_joiner = TRUE
-		mind.active = 0					//we wish to transfer the key manually
+		mind.active = FALSE					//we wish to transfer the key manually
 		mind.transfer_to(H)					//won't transfer key since the mind is not active
 		mind.original_character = H