This commit removes the HWProbes() function from the console and tty
packages and replaces it with a global ProbeFuncs slice which is fetched
by the hal package when the hardware autodetection code runs.
Each driver should provide an init() function that appends a probe function
to the global ProbeFuncs slice.
This approach allows us to support conditional compilation of drivers in
the future (e.g. using build tags)
This commit refactors the old VT implementation to work with the revised
TTY interface and adds support for:
- scrollback
- terminal state handling
When a terminal becomes activated, it overwrites the attached console
contents with the contents of its viewport.
