Add an option for a tree hierarchy view

**Is your feature request related to a problem? Please describe.**
It is a hazzle to view multiple entries in different groups and since the first time I of starting KeePassDX (coming from KeePassXC) I am getting confused with the arrow on the left side of each Group, which serves no functional purpose, other then to visualize a group entry.

**Describe the solution you'd like**
It would be good to implement an option to trigger a different view mode, which allows for the visualization of subgroups and -entries. The arrow would rotate and show the entries underneath, while the inner view for all entries must be configured to be able to slide left and optionally snap to the right side of the last opened entry.

**Describe alternatives you've considered**
The view must not snap, if inconvinient. But I do not think of an alternative, as the only other efficient solution is implemented atm. Showing the subentries in a temporary window would not allow for a recursive hierarchy and nothing else came to my head. This solution is also implemented in probably any desktop-file-browser and also KeePassXC.

**Additional context**
It needs time and resources to find multiple entries with unknowm names, which is a hazzle for any hardcore-user. It would benefit a lot and help with headpain when using the app to often. People actually work on their phones so why not make it easier ;)

The issue does not name implementation files, tests, or an entry point. Start by reviewing the current group and entry view, then define the hierarchy, expansion, sliding, and snapping behavior before identifying the Android UI components and tests needed to verify the completed view.

Written by the indexing model from the issue text.