FEATURE: new jump to channel menu (#22383)

This commit replaces two existing screens:
- draft
- channel selection modal

Main features compared to existing solutions
- features are now combined, meaning you can for example create multi users DM
- it will show users with chat disabled
- it shows unread state
- hopefully a better look/feel
- lots of small details and fixes...

Other noticeable fixes
- starting a DM with a user, even from the user card and clicking <kbd>Chat</kbd> will not show a green dot for the target user (or even the channel) until a message is actually sent
- it should almost never do a full page reload anymore

---------

Co-authored-by: Martin Brennan <mjrbrennan@gmail.com>
Co-authored-by: Jordan Vidrine <30537603+jordanvidrine@users.noreply.github.com>
Co-authored-by: chapoi <101828855+chapoi@users.noreply.github.com>
Co-authored-by: Mark VanLandingham <markvanlan@gmail.com>

plugins/chat/test/javascripts/components/chat-user-avatar-test.js

@@ -37,7 +37,7 @@ module("Discourse Chat | Component | chat-user-avatar", function (hooks) {
     });
 
     await render(
-      hbs`<ChatUserAvatar @chat={{this.chat}} @user={{this.user}} />`
+      hbs`<ChatUserAvatar @showPresence={{true}} @chat={{this.chat}} @user={{this.user}} />`
     );
 
     assert.true(