Improve timestamp display in the chatview

Design reference

added ui/ux label

Group messages per day & time

assigned to @nvengeon

added sprintto review label

https://review.jami.net/c/jami-client-qt/+/22414

mentioned in commit d6ed9adf

Please see #852 (closed). Haven't been able to check Yesterday string. Thank you

@abandali is on it. Strings are fine and translatable, just something with the CI

added sprintdone label and removed sprintto review label

closed

removed sprintdone label

mentioned in commit 61ccbdf4