#5133 Fix broken email threading for draft messages

[martgil]

This PR fixes the broken email threading for FlowCrypt's secure draft messages.

close #5133

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Tests (delete all except exactly one):

• Does not need tests (refactor only, docs or internal changes)

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To be filled by reviewers

I have reviewed that this PR... (tick whichever items you personally focused on during this review):

• addresses the issue it closes (if any)
• code is readable and understandable
• is accompanied with tests, or tests are not needed
• is free of vulnerabilities
• is documented clearly and usefully, or doesn't need documentation

[martgil]

Hi @sosnovsky - this one is ready for review. Thank you!

Please follow the manual test below:

1. User 1 send to user 2,3 using FlowCrypt (via to, cc would work too).
2. As user 2, compose a secure reply -> go back to make a draft.
3. Access the draft from Gmail's draft folder.
4. Send the secure email reply.

[martgil]

This change goes to correct the logic of the existing code. Since the last container of the message to obtain the msgId does not mean to be where the container where the secure compose get's clicked.

What I mean by is, assume there are several existing converstations in an email thread (doesn't matter if its a group message). Assume the user clicks secure reply for a specific email that is placed in the middle order of the converstation, this will access the appropriate container rather than the last container of the conversation of the opened email thread.