Missing presence value in `presence-changed` event for initial presence

[chacha912]

What happened:

When a user sets an initial presence while attaching a document, a presence-changed event is triggered with an undefined presence value. This is because when publishing the presence-changed event, the presence is retrieved using getPresence, which only returns presence for online clients.

What you expected to happen:

The value of the presence-changed event should include the initial presence value set by the user.

How to reproduce it (as minimally and precisely as possible):

Execute following code:

it.only('initial presence', async function ({ task }) {
  const c1 = new yorkie.Client(testRPCAddr);
  await c1.activate();
  const c1ID = c1.getID()!;

  const docKey = toDocKey(`${task.name}-${new Date().getTime()}`);
  const events1 = new EventCollector<DocEvent>();
  type PresenceType = { key: string };
  const doc1 = new yorkie.Document<{}, PresenceType>(docKey);
  const unsub1 = doc1.subscribe('presence', (event) => events1.add(event));

  await c1.attach(doc1, {
    initialPresence: { key: 'val1' },
  });

  await events1.waitAndVerifyNthEvent(1, {
    type: DocEventType.PresenceChanged,
    value: { clientID: c1ID, presence: { key: 'val1' } },  // presence value is missing 
  });

  unsub1();
});

Anything else we need to know?:

Related: yorkie-team/yorkie#671

Environment:

• Operating system:
• Browser and version:
• Yorkie version (use yorkie version):
• Yorkie JS SDK version: