Merge branch 'improve-conversation-loading-performance' into 'mainline'

Improve conversation loading performance

See merge request !181

(cherry picked from commit 940241bb)

ca399921 conversation: update GUI every 10 mails
5 jobs for cherry-pick-940241bb in 26 minutes and 3 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #266263
fedora

00:10:24

passed #266264
ubuntu

00:03:02

 
  Test
passed #266265
flatpak

00:14:24

 
  Deploy
passed #266266
review

00:00:32

passed #266267
allowed to fail manual
stop_review

00:00:41