mimefactory: place common IMF headers at the top of the message

This moves most common headers like From, To, Subject etc. defined in
the Internet Message Format standard at the top of the message
in the same order as used in RFC 5322.

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Changes
 - add more SMTP logging #3093
+- place common headers like `From:` before the large `Autocrypt:` header #3079
 
 
 ## 1.76.0