Converts A && A.B into A?.B (#54342)

Implements the ?. operator, replacing code like A && A.B with A?.B

BYOND Ref:
When reading A?.B, it's equivalent to A && A.B except that A is only evaluated once, even if it's a complex expression like a proc call.

code/modules/admin/verbs/mapping.dm

@@ -242,7 +242,7 @@ GLOBAL_LIST_EMPTY(dirty_vars)
 		if(istype(A,type_path))
 			var/atom/B = A
 			while(!(isturf(B.loc)))
-				if(B && B.loc)
+				if(B?.loc)
 					B = B.loc
 				else
 					break