[path/filepath] Change join() to take a []string instead of varargs

This makes passing an allocator easier, as you no longer have to resort to
named arguments:
Before:
  `join(a, b, c)` became `join(elems={a, b, c}, allocator=ally)`
After:
  `join({a, b, c})` becomes `join({a, b, c}, ally)`

core/path/filepath/match.odin

@@ -305,7 +305,7 @@ _glob :: proc(dir, pattern: string, matches: ^[dynamic]string, allocator := cont
 		n := fi.name
 		matched := match(pattern, n) or_return
 		if matched {
-			append(&m, join(dir, n))
+			append(&m, join({dir, n}))
 		}
 	}
 	return