conversation view in inbox and message screen

[tomholub]

this will be a big one - we'll get to this when all of the basics are done

[tomholub]

part of #714

[tomholub]

I'd like to consider a simpler version of this issue.

Did you say there was an issue managing more than one webview on a screen?

To simplify, we could consider:

• only use conversation view in inbox when Gmail API is used. This means that inbox items will be equivalent between FlowCrypt app and Gmail app
• when I click a conversation, render a similar conversation list that Gmail renders, where I can click and unpack individual messages in conversation, with the following changes compared to Gmail app:
  • only one email at a time can be unpacked (unpacking another email will pack the previously unpacked email)
  • by default, always unpack the first unread email in the conversation (which contains quoted previous emails anyway - usually)