update appium dependencies

From v6.x.x to v7.x.x equivalents, and adjust codebase if needed (in one PR). The updates may contain some stability fixes.

<img width="1139" alt="image" src="https://user-images.githubusercontent.com/6306961/138921625-bc2a73b3-917a-4543-b342-5dbf6badd730.png">

_Originally posted by @tomholub in https://github.com/FlowCrypt/flowcrypt-ios/issues/769#issuecomment-952110664_