Layout issues with AppContentDetail display

[jancborchardt]

Some issues with the layout / text display of the Mail content area:

• [ ] The subline has an unnecessary line break when the text is long. It should be ellipsized here. (Currently the subject is shown here, but will be the first line of the email with https://github.com/nextcloud/mail/issues/2579 )
• [ ] The "Reply all" label has an unnecessary line break here, probably caused by the long text of the subline. Ideally this should not influence each other :)
• [ ] The subline is shown in color-main-text but we usually show it in color-text-maxcontrast
• [ ] The timestamp is shown in color-main-text but we usually show it in color-text-maxcontrast

cc @GretaD and @ChristophWurst because Greta is on holiday.