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/view_variables/mass_edit_variables.dm

@@ -8,7 +8,7 @@
 	if(!check_rights(R_VAREDIT))
 		return
 
-	if(A && A.type)
+	if(A?.type)
 		method = vv_subtype_prompt(A.type)
 
 	src.massmodify_variables(A, var_name, method)
@@ -114,7 +114,7 @@
 			var/list/varsvars = vv_parse_text(O, new_value)
 			var/pre_processing = new_value
 			var/unique
-			if (varsvars && varsvars.len)
+			if (varsvars?.len)
 				unique = alert(usr, "Process vars unique to each instance, or same for all?", "Variable Association", "Unique", "Same")
 				if(unique == "Unique")
 					unique = TRUE

code/modules/admin/view_variables/modify_variables.dm

@@ -23,7 +23,7 @@ GLOBAL_PROTECT(VVpixelmovement)
 	var/list/subtypes = subtypesof(type)
 	if (!subtypes || !subtypes.len)
 		return FALSE
-	if (subtypes && subtypes.len)
+	if (subtypes?.len)
 		switch(alert("Strict object type detection?", "Type detection", "Strictly this type","This type and subtypes", "Cancel"))
 			if("Strictly this type")
 				return FALSE