refactor: use contextual empty slice literals

std/hashmap/hashmap.hon

@@ -46,7 +46,7 @@ init proc(
     allocator mem.Allocator,
 ) HashMap(K, V, hash_key, keys_eql) {
     return HashMap(K, V, hash_key, keys_eql){
-        entries = mem.empty(Entry(K, V)),
+        entries = &[],
         count = 0,
         allocator = allocator,
     }