Keep original reply message when switching to secure mode

[sosnovsky]

• open thread with multiple messages (including encrypted). for example, #5004 cryptup_reply div not hidden issue thread in flowcrypt.compatibility inbox
• click reply button in the toolbar of the first message
• compose box appears with red banner
• click Switch to encrypted reply
• secure compose box is loaded
• click ... to show quoted content of the previous messages
• it'll include content of all thread messages, while it's expected to have quoted content only of the first message as reply is composed to it

probably worked well in 8.5.6

+ implement ui test