[APP-737] Accessible native dropdown menu (#988)

* fix comments

* add zeego package

* get basic native dropdown working

* add separator and icon components

* refined native dropdown component

* add android build properties to app.json

* move `PostDropdownBtn` to its own component

* fix selectors issue

* move `PostDropdownBtn` to its own component

* fix hitslop

* fix post dropdown hitslop

* fix android dropdown icons

* move `UserAvatar.tsx` to native dropdown

* use native dropdown in `ProfileHeader.tsx`

* use native dropdown in `PostThreadItem.tsx`

* use native dropdown in `UserBanner.tsx`

* use native dropdown in `CustomFeed.tsx`

* replace `testId` with `testID` (which is what is used everywhere)

* move `Settings.tsx` to use native dropdown

* create jest mocks for zeego

* create jest mock for `zeego/dropdown-menu`

* web styles for native dropdown

* remove example native dropdown

* adjust web styles

* fix propagation

* fix pressable in `Settings.tsx`

* animate dropdown on web

* add keyboard nav and hover styles

* add hitslop to constants

* add comments to NativeDropdown component

* temporarily removed android icons

* add testID to PostDropdownBtn

* add testID back to all NativeDropdown button implementations

* add postDropdownBtn testID

* add testID to dropdown items

* remove testID from dropdown menu item

* refactor home-screen tests for native dropdown

* refactor profile-screen tests for native dropdown

* refactor thread-muting tests for native dropdown

* refactor thread-screen tests for native dropdown

* fix dropdown color for post dropdown button

* remove icons from android dropdown menu

* fix `create-account.test.ts`

* fix `invite-codes.test.ts`

__mocks__/zeego/dropdown-menu.js

@@ -0,0 +1,2 @@
+export const DropdownMenu = jest.fn().mockImplementation(() => {})
+export const create = jest.fn().mockImplementation(() => {})