- A repaint will always occur from a lookAndFeelChanged

- 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 is a breaking change - see BREAKING-CHANGES.txt

This fixes an issue where opening a FileTreeComponent could cause the UI
to hang. The call to subcontentsList->isStillLoading() in
FileListTreeItem::selectFile() would always return true because the
file-scanner TimeSliceThread wasn't started until the selectFile() call
finished.

When bridging 32-bit/64-bit plugins on Windows, the plugin is hosted in
an auxilliary process, and the plugin's editor is embedded into an HWND
owned by a different process (the plugin host).

Previously, the `isForegroundProcess` check would fail for bridged
plugins, because the foreground window may belong to the DAW, rather
than to the auxilliary hosting process.

This patch adds an additional check, to find whether the same process
owns both the foreground window, and the window which embeds the
PopupMenu's target component. In this case, we avoid immediately
dismissing the PopupMenu.