This makes the ordering consistent with other view modes of the
FileBrowserComponent and restores the behaviour prior to a400d3ebe0.

This fixes a regression introduced in
a400d3ebe0.

Previously when using the FileBrowserComponent in TreeView mode, a
refresh would delete all items and rebuild the UI based on new
directory scan data, losing the openness state in the process. With
this commit only changes are applied to the current TreeView.

- Created a new detail namespace
- Moved shared module implementation details into the detail namespace
- Split dependencies so source files only rely on details in the detail namespace
- Removed all code from the juce_gui_basics.cpp file

This fixes warnings that are emitted when building with the `-analyze`
flag enabled.