Add latency graph command (#2359)

* add latency graph command

* fix coding style

* Clean code

* use "enable-debug-command" is redis 7+ only

* Update LATENCY_GRAPH.spec.ts

Co-authored-by: Leibale Eidelman <me@leibale.com>

packages/client/lib/commands/LATENCY_GRAPH.spec.ts

@@ -0,0 +1,32 @@
+import { strict as assert } from 'assert';
+import testUtils, { GLOBAL } from '../test-utils';
+import { transformArguments } from './LATENCY_GRAPH';
+
+describe('LATENCY GRAPH', () => {
+    it('transformArguments', () => {
+        assert.deepEqual(
+            transformArguments('command'),
+            [
+                'LATENCY',
+                'GRAPH',
+                'command'
+            ]
+        );
+    });
+
+    testUtils.testWithClient('client.latencyGraph', async client => {
+        await Promise.all([
+            client.configSet('latency-monitor-threshold', '1'),
+            client.sendCommand(['DEBUG', 'SLEEP', '0.001'])
+        ]);
+
+        assert.equal(
+            typeof await client.latencyGraph('command'),
+            'string'
+        );
+    }, {
+        serverArguments: testUtils.isVersionGreaterThan([7]) ?
+            ['--enable-debug-command', 'yes'] :
+            GLOBAL.SERVERS.OPEN.serverArguments
+    });
+});