[native] Displaying edit mode

Summary: Added displaying edit GUI when in edit mode.

Test Plan:
Checked if after clicking 'Edit' on the target message edit mode is turned on.
Checked if the displayed content of the edited message work in different situations:

• if the original message is already edited,
• if the original message has some markdown,
• if the original message is really long/multiline,
• if the original message has replies/quotes,

With already edited content:

On Android:

Reviewers: michal, inka, ginsu, tomek

Reviewed By: tomek

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D7344