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/language/method/static.wren

@@ -3,8 +3,8 @@ class Foo {
   bar { "on instance" }
   static bar { "on metaclass" }
 
-  bar(arg) { "on instance " + arg }
-  static bar(arg) { "on metaclass " + arg }
+  bar(arg) { "on instance %(arg)" }
+  static bar(arg) { "on metaclass %(arg)" }
 }
 
 System.print(Foo.new().bar)        // expect: on instance