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 previous implementation would trigger assertions in
grabKeyboardFocus() when the DragImageComponent was hidden due to the
target returning false from shouldDrawDragImageWhenOver().

Hiding the image would also mean that its keyboard focus was lost. Now
focus is restored when the image becomes visible again.

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.

This new factoring is a bit more typesafe, as it avoids casting
internals to void*.

It also allows cursors to scale appropriately on high resolution
displays on Windows.

This commit removes the various compiler-specific JUCE_DEPRECATED macros and replaces them with C++14's deprecated attribute. It also removes the JUCE_CATCH_DEPRECATED_CODE_MISUSE flag as we can rely on the override specifier catching usage of these old virtual methods, and tidies up the DOXYGEN preprocessor checks as they were inconsistent across the codebase.