Organize symbols by deck in the symbols browser

[zuevval]

Users said it would be convenient if the symbols were organized into decks in the browser to make it easier to navigate them (see the roadmap, second point in "asked to improve").

They say TalkBack features a special gesture for navigating headers (an example of the application with headers: Sberbank Online). What I'd like to do is to try two different ways:

• [x] make nested menus with RecyclerView
• make drop-down lists (approximately as in the iOS app)
• [ ] Then ask V.N. and others (Alexei Viktorovich, for instance) to test

[zuevval]

Most likely, I will not do the second implementation