Add httl and integrate in hexpire test

Context: redis#1324 (comment)

`httl` documentation: https://redis.io/docs/latest/commands/httl/

Author: vietqhoang

lib/redis/commands/hashes.rb

@@ -267,6 +267,20 @@ def hscan_each(key, **options, &block)
       def hexpire(key, ttl, *fields)
         send_command([:hexpire, key, ttl, 'FIELDS', fields.length, *fields])
       end
+
+      # Returns the time to live in seconds for one or more fields.
+      #
+      # @example
+      #   redis.hset("hash", "f1", "v1", "f2", "v2")
+      #   redis.hexpire("hash", 10, "f1") # => [1]
+      #   redis.httl("hash", "f1", "f2", "f3") # => [10, -1, -2]
+      #
+      # @param [String] key
+      # @param [Array<String>] fields
+      # @return [Array<Integer>] The number of fields that were added to the hash
+      def httl(key, *fields)
+        send_command([:httl, key, 'FIELDS', fields.length, *fields])
+      end
     end
   end
 end

test/lint/hashes.rb

@@ -232,12 +232,8 @@ def test_hexpire
       target_version "7.4.0" do
         r.hset("foo", "f1", "v2")
 
-        assert_equal [1], r.hexpire("foo", 1, "f1")
-        assert r.hexists("foo", "f1")
-
-        sleep(1)
-
-        refute r.hexists("foo", "f1")
+        assert_equal [1], r.hexpire("foo", 4, "f1")
+        assert_in_range(1..4, r.httl("foo", "f1")[0])
       end
     end
   end