feat: implement map literal syntax with curly braces and DUP bytecode

Add support for map literals using `{}` syntax in the compiler, replacing the previous `new Map` constructor pattern. This introduces a new `map()` grammar function that loads the Map class, instantiates it, and compiles key-value pairs using subscript setter calls. A new `CODE_DUP` bytecode is added to duplicate the map reference on the stack for each element insertion. The change includes updated test files to use literal syntax and new error tests for edge cases like EOF after colon, comma, key, or value.

test/map/eof_after_comma.wren

@@ -0,0 +1,2 @@
+var map = {1: 2,
+// expect error