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/module/cyclic_import/a.wren

@@ -2,8 +2,8 @@
 System.print("start a")
 
 var A = "a value"
-System.print("a defined " + A)
+System.print("a defined %(A)")
 import "b" for B
-System.print("a imported " + B)
+System.print("a imported %(B)")
 
-System.print("end a")
+System.print("end a")

test/language/module/cyclic_import/b.wren

@@ -2,8 +2,8 @@
 System.print("start b")
 
 var B = "b value"
-System.print("b defined " + B)
+System.print("b defined %(B)")
 import "a" for A
-System.print("b imported " + A)
+System.print("b imported %(A)")
 
 System.print("end b")

test/language/module/shared_import/a.wren

@@ -1,5 +1,5 @@
 // nontest
 System.print("a")
 import "shared" for Shared
-var A = "a " + Shared
+var A = "a %(Shared)"
 System.print("a done")

test/language/module/shared_import/b.wren

@@ -1,5 +1,5 @@
 // nontest
 System.print("b")
 import "shared" for Shared
-var B = "b " + Shared
+var B = "b %(Shared)"
 System.print("b done")