feat: add remove() method to Map class with native implementation and tests

test/map/remove.wren

@@ -0,0 +1,18 @@
+var map = {
+  "one": 1,
+  "two": 2,
+  "three": 3
+}
+
+IO.print(map.count) // expect: 3
+IO.print(map.remove("two")) // expect: 2
+IO.print(map.count) // expect: 2
+IO.print(map.remove("three")) // expect: 3
+IO.print(map.count) // expect: 1
+
+// Remove an already removed entry.
+IO.print(map.remove("two")) // expect: null
+IO.print(map.count) // expect: 1
+
+IO.print(map.remove("one")) // expect: 1
+IO.print(map.count) // expect: 0