Add unlisted visibility on Long click

[tribela]

A lot of people want to use "unlisted" visibility. But @Gargron said that

This option has been omitted on purpose since it overlaps with public in almost all ways. We keep the dropdown simple, with all other options being very intuitive to understand.

So this PR keeps that dropdown menu simple, but few changes.

• Show unlisted visibility only when unlisted is selected (hidden by default) (eg, replying to unlisted post)
• Change visibility setting to "unlisted" when long pressed privacy menu (Like hidden feature)

https://user-images.githubusercontent.com/5047683/170216453-3678b34b-2e04-42a3-8b62-a3dad7c644f4.mp4