feat: implement string interpolation with %(expr) syntax in compiler and core library

Add lexer support for `TOKEN_INTERPOLATION` to split string literals at interpolation points, introduce `MAX_INTERPOLATION_NESTING` limit of 8, and compile interpolated strings by emitting calls to `String.interpolate_()`. Optimize list and map literal construction with new `addCore_` primitives to reduce stack churn. Update `String`, `List`, and `Map` `toString` methods in core library to use interpolation syntax, and migrate all benchmark and test files from explicit concatenation to interpolated strings.

test/api/foreign_class.wren

@@ -30,7 +30,7 @@ foreign class Point is PointBase {
   }
 
   construct new(x, y, z) {
-    System.print(x.toString + ", " + y.toString + ", " + z.toString)
+    System.print("%(x), %(y), %(z)")
   }
 
   foreign translate(x, y, z)