Change old slot syntax (removed in vue3) to new one

In addition it fixes some semi-related issues:

• Several places where popover is used trigger wasn't a <button>, changed to button.
  • exception - ModifiedIndicator, since it's not really interactive, used aria-label instead to make it accessible and NOT generate a tooltip.
• Timeline menu (the dropdown home/dms/local/etc switcher) was using panel panel-default classes, switched it to popover-default so that it uses tooltips background (has separate opacity from panels for better visibility)
• Excessive <div>s that don't do anything replaced with <template>s

added 1 commit

• 61dcdbf9 - migrate to v-slot

Compare with previous version

changed the description

requested review from @shpuld

there's a few new warnings introduced (I just check the build job on gitlab) that should be fixed, otherwise if you've tested the affected components that nothing's accidentally broken, looks all good

resolved all threads

added 1 commit

• 80220c1b - fix warnings

Compare with previous version

enabled an automatic merge when the pipeline for 80220c1b succeeds

merged

mentioned in commit 0ca0e642

changed milestone to %Vue 3 support