Add the ability to reply to a message (#7170)

Feature
- [x] Allow to click on reply to go to the real message
    - [x] In chat
- [x] Show only a part of the message that you reply to
    - [x] In chat
    - [x] In reply preview

TODO’s
- [x] Fix migration
    - [x] timestamp(in filename)
    - [x] remove the reference to the reply_message_id
- [x] Fix markdown cache for reply message
- [x] Fix spacing when first message is a reply to you and you want to
reply to that message.
- [x] Fetch message that you replied to
    - [x] allow fetching messages that are not inside the current view 
- [x] When message is deleted, we should show a text like `message
deleted` or something
    - [x] Show correct GitHub username + icon after `Replied to: `
    - [x] Show correct message(now it's hard-coded)
- [x] Add icon to reply + add the onClick logic
- [x] Show message that you want to reply to
  - [x] Allow to click away the message that you want to reply to
  - [x] Fix hard-coded GitHub user + icon after `Reply tp:`
  - [x] Add tests

<img width="242" alt="Screenshot 2024-02-06 at 20 51 40"
src="https://github.com/zed-industries/zed/assets/62463826/a7a5f3e0-dee3-4d38-95db-258b169e4498">
<img width="240" alt="Screenshot 2024-02-06 at 20 52 02"
src="https://github.com/zed-industries/zed/assets/62463826/3e136de3-4135-4c07-bd43-30089b677c0a">


Release Notes:

- Added the ability to reply to a message.
- Added highlight message when you click on mention notifications or a
reply message.

---------

Co-authored-by: Bennet Bo Fenner <53836821+bennetbo@users.noreply.github.com>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/collab/src/tests/channel_message_tests.rs

@@ -43,6 +43,7 @@ async fn test_basic_channel_messages(
                 MessageParams {
                     text: "hi @user_c!".into(),
                     mentions: vec![(3..10, client_c.id())],
+                    reply_to_message_id: None,
                 },
                 cx,
             )
@@ -402,3 +403,66 @@ async fn test_channel_message_changes(
 
     assert!(b_has_messages);
 }
+
+#[gpui::test]
+async fn test_chat_replies(cx_a: &mut TestAppContext, cx_b: &mut TestAppContext) {
+    let mut server = TestServer::start(cx_a.executor()).await;
+    let client_a = server.create_client(cx_a, "user_a").await;
+    let client_b = server.create_client(cx_b, "user_b").await;
+
+    let channel_id = server
+        .make_channel(
+            "the-channel",
+            None,
+            (&client_a, cx_a),
+            &mut [(&client_b, cx_b)],
+        )
+        .await;
+
+    // Client A sends a message, client B should see that there is a new message.
+    let channel_chat_a = client_a
+        .channel_store()
+        .update(cx_a, |store, cx| store.open_channel_chat(channel_id, cx))
+        .await
+        .unwrap();
+
+    let channel_chat_b = client_b
+        .channel_store()
+        .update(cx_b, |store, cx| store.open_channel_chat(channel_id, cx))
+        .await
+        .unwrap();
+
+    let msg_id = channel_chat_a
+        .update(cx_a, |c, cx| c.send_message("one".into(), cx).unwrap())
+        .await
+        .unwrap();
+
+    cx_a.run_until_parked();
+
+    let reply_id = channel_chat_b
+        .update(cx_b, |c, cx| {
+            c.send_message(
+                MessageParams {
+                    text: "reply".into(),
+                    reply_to_message_id: Some(msg_id),
+                    mentions: Vec::new(),
+                },
+                cx,
+            )
+            .unwrap()
+        })
+        .await
+        .unwrap();
+
+    cx_a.run_until_parked();
+
+    channel_chat_a.update(cx_a, |channel_chat, _| {
+        assert_eq!(
+            channel_chat
+                .find_loaded_message(reply_id)
+                .unwrap()
+                .reply_to_message_id,
+            Some(msg_id),
+        )
+    });
+}