Fix error when HashMap.remove on uninitialized HashMap (#1629)

* HashMap: test removal on uninitialized

* HashMap.remove_entry_for_key: return false on unintialized

* test: switch to temp_init

* release note

test/unit/stdlib/collections/map.c3

@@ -53,4 +53,14 @@ fn void map()
         assert(tc.key == list[i].key);
         assert(tc.value == list[i].value);
     }
-}
+}
+
+fn void map_remove()
+{
+	Map m;
+	assert(!@ok(m.remove("A")));
+	m.temp_init();
+	assert(!@ok(m.remove("A")));
+	m.set("A", 0);
+	assert(@ok(m.remove("A")));
+}