- 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

When the mouse moves from one window to another, the mouseExit event
for the old window can occur after the mouseMove event for the new.
Until this commit this would cause the MouseInputSource to be
associated with the old window, and getComponentUnderMouse() would
incorrectly return a nullptr.

The bug was triggered on Monterey where a pressure of 1 is reported
while a mouse button is being held down. This caused an extra drag
event being triggered between mouse down and up events, even if no
movement occurred.