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/count.wren

@@ -1,4 +1,4 @@
-var map = new Map
+var map = {}
 IO.print(map.count) // expect: 0
 map["one"] = "value"
 IO.print(map.count) // expect: 1

test/map/eof_after_colon.wren

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

test/map/eof_after_comma.wren

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

test/map/eof_after_key.wren

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

test/map/eof_after_value.wren

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

test/map/grow.wren

@@ -58,7 +58,7 @@ var fishes = [
   "Cutlassfish", "Cutthroat eel", "Cutthroat trout"
 ]
 
-var map = new Map
+var map = {}
 for (fish in fishes) {
   map[fish] = fish.count
 }

test/map/key_types.wren

@@ -1,13 +1,13 @@
-var map = new Map
-
-map[null] = "null value"
-map[true] = "true value"
-map[false] = "false value"
-map[0] = "zero"
-map[1.2] = "1 point 2"
-map[List] = "list class"
-map["null"] = "string value"
-map[1..3] = "1 to 3"
+var map = {
+  null: "null value",
+  true: "true value",
+  false: "false value",
+  0: "zero",
+  1.2: "1 point 2",
+  List: "list class",
+  "null": "string value",
+  (1..3): "1 to 3"
+}
 
 IO.print(map[null]) // expect: null value
 IO.print(map[true]) // expect: true value

test/map/type.wren

@@ -1,7 +1,5 @@
-// TODO: Use map literal.
-
-IO.print(new Map is Map)      // expect: true
+IO.print({} is Map)      // expect: true
 // TODO: Abstract base class for associations.
-IO.print(new Map is Object)    // expect: true
-IO.print(new Map is Bool)      // expect: false
-IO.print((new Map).type == Map) // expect: true
+IO.print({} is Object)    // expect: true
+IO.print({} is Bool)      // expect: false
+IO.print({}.type == Map) // expect: true