Feature: roll selected messages

User story: it is hard to realize which messages are selected if they don't fit in one screen. So it would be helpful to have a possibility to check selected messages.

Proposal: roll selected messages one by one clicking the widget showing selected messages amount.

Commit: https://github.com/lordfess/Telegram/commit/85e676e3cf80843f6c5a7f98ef322c1f3cd8d71a

Feature: use navigation back stack for jumping back from replies or pinned messages

User story:
1. If you enter to a chat having unread messages and scroll to a pinned message, you don't have an opportunity going back.
2. If you flow through replies on messages you don't have an opportunity going back the same way.
3. You can combine #1 and #2 in different ways

Proposal:
1. Store all user message jumps and allow going back by clicking page down button.
2. Clear back stack for some reason (scroll to the message list bottom, unordinary jumps, etc).
3. Allow clean stack with scroll to the message list bottom by page down button long click.

Commit:
https://github.com/lordfess/Telegram/commit/ffc16d1271a855e99a2ce0c1d8ef62315535cbfd

Fix: forward to the saved message if chats have been updated

Steps to reproduce:
1. Delete saved messages chat
2. Go to a chat and select a message or messages
3. Click the forward button. You should stay on the chat list with out any actions.
4. Wait before a new message in a chat
5. Select saved messages chat for forwarding
6. Sometimes the saved messages chat goes to the chat list bottom and has got incorrect rendering

Expected behavior:
Saved messages chat should be ordered by time

Commit:
https://github.com/lordfess/Telegram/commit/5111bd3553834666301a79bceaee7f0b22840fb7

Feature: camera2 API support

User story: using a new camera API instead of deprecated one

Proposal:
1. Move all calls to explicit types to interfaces
2. Use camera2 API if platform API version high enough (at least 21)
3. Leave all code outside the camera package as the same as possible with the same functionality
4. Easy way to add a new camera API (e.g. CameraX) - just implement 3 interfaces.

Issues:
1. Time to time a shot takes much time. The reason is long AE/AF converging process (actually google camera app has the same behavior). There should be a timeout for capturing time.

Tested on devices: Pixel 3 (API 30), Samsung Galaxy 8 (API 26), Samsung G350E (API 19)

Commit:
https://github.com/lordfess/Telegram/commit/25362db141dcb8aa8c7d6453f0b063da47b221d8

Всего исправлений и улучшений: 4 
Из них корректных: 2

#1: Возможность перехода между непрочитанными сообщениями не учитывает, в какой позиции в данный момент находится скролл.

#2: Смена ориентации устройства перерисовывает интерфейс камеры с задержкой (Nexus 5X). При первой смене ориентации девайса после запуска приложения экран может смаргивать белым. 

#3: Если несколько раз подряд нажать кнопку затвора, он может не активироваться вообще или привести к вылету приложения (Samsung Galaxy J7 Android 9). 

Функциональность записи видеосообщений не работает. 

UPD. Просим прощения за неточность комментария о видеосообщениях — проблема, с которой мы часто сталкивались в ходе тестирования, идентична #issue12026.

1) Works, very useful!
2) Works, very useful!
3) I did not find the change.

The camera is corrupted. If I take a shot in portrait mode it's taking in landscape mode while displaying

Okay then you could dm me?

I meant that you could direct message me on Telegram for better discussion about the issue if you don't mind

Nice camera rework, but found 2 small issues.

1. Sometimes instant video recording output is incorrectly cropped. This can reproduced when the phone is lying horizontally. Also stopping instant recording seem to block UI thread.
2. Usual video recording goes with some UI thread blocks