Dolphin settings re-layout (small scope)

Motivation: After a user asked a question in the general KDE chat, where they wouldn't find the setting to make folder size use the content sizes, I started looking for it, and was kind of surprised that it belongs to the Details View. Trying to find a better place for it, I stumbled upon the different settings pages and came out with this proposal.

Note that the scope is small, and it simply tries to move some settings around and re-group them a more (IMHO) logical place to improve the situation in a manageable short-term. Larger scoped refactors can take longer time to agree on and have a higher risk of bike-shedding 😄

Page	Current Status	Rationale/Proposal
General->StatusBar		Replace StatusBar with a new Appearance tab. Then these settings become just a group in the Appearance tab
General->Behavior		Move Show.. to thenew Appearance tab. Move the SplitView related settings to Navigation
Startup		The initial settings affect the initial status when open dolphin. The latter ones on the other hand are general settings that can be grouped intp Appearance or Navigation
Navigation		Just to show how much unused real state this page has 😄 and specially how other settings can fit here perfectly
View Modes->DetailsView		These two settings also affect other views and places (while maybe they are more niche): - when sorting/grouping by size - adding more fields to those views ('Add More Information > ...') - on the Information Panel: we always show the relative dates irrespective of this setting Proposal: Move Folder Size to General->Behavior Move Display Date to General->Appearance

Pinging @felixernst, @meven and @ngraham on a first round to get a general feel whether this a direction we want to go to and it's worth to start working on it.

I also kind of recall there has been some (recent?) proposal on this same topic. Sorry if this stepping into some work-on-progress. I couldn't quickly find a reference to that work.