Remove ConversationView.add_reply_from_reply_box

[redshiftzero]

Description

Fixes #821.

I had a suspicion that adding widgets to the conversation view outside of ConversationView.update_conversation might be a cause for the odd bubbles appearing on top of each other behavior that some are seeing (I've not seen this myself yet), so putting this diff up which I had locally (because I don't think this method is required anymore) in case it's related to that. Will look more tomorrow to try to reproduce the underlying behavior if no one beats me to it.

Test Plan

Check you can still send replies and they are confirmed as usual

Checklist

If these changes modify code paths involving cryptography, the opening of files in VMs or network (via the RPC service) traffic, Qubes testing in the staging environment is required. For fine tuning of the graphical user interface, testing in any environment in Qubes is required. Please check as applicable:

• I have tested these changes in the appropriate Qubes environment
• I do not have an appropriate Qubes OS workstation set up (the reviewer will need to test these changes)
• These changes should not need testing in Qubes

If these changes add or remove files other than client code, packaging logic (e.g., the AppArmor profile) may need to be updated. Please check as applicable:

• I have submitted a separate PR to the packaging repo
• No update to the packaging logic (e.g., AppArmor profile) is required for these changes
• I don't know and would appreciate guidance

[eloquence]

Checked in with @redshiftzero about this PR before her leave; this is still a valuable change, we can pick this up from her in coming weeks.

[sssoleileraaa]

I just updated the work that @redshiftzero did to get it ready for review. I don't think it fixes an error at this point, but it is a nice refactor that simplifies our logic around adding reply widgets. I tried to change very little so that this remains a simply refactor.

[sssoleileraaa]

@rocodes - Feel free to test this alongside #1432, it's still a WIP, which you can take over, review, or just incorporate it into #1432. After today's conversation, I think this could help separate out some of the complexity around reply widgets for draftreplies.

[sssoleileraaa]

(tests should fail because I didn't even run them locally yet after my update)

[rocodes]

This is a nice change that definitely simplifies the reply and draft logic, tests look good, and replies still show up in the reply box.

I did once notice a reply that seemed to briefly disappear after being sent and re-appear on sync, but I haven't been able to reproduce it despite a lot of attempts. I also noticed this issue, but it's not a regression since it's also present on main.

From a preliminary review it looks good to me.

[sssoleileraaa]

Closing because commits from here are being cherry-picked into #1432