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/limit/interpolation_nesting.wren

@@ -0,0 +1 @@
+System.print("0 %("1 %("2 %("3 %("4 %("5 %("6 %("7 %(8)")")")")")")")") // expect: 0 1 2 3 4 5 6 7 8

test/limit/too_much_interpolation_nesting.wren

@@ -0,0 +1 @@
+System.print("0 %("1 %("2 %("3 %("4 %("5 %("6 %("7 %("8 %(9)")")")")")")")")") // expect error