clients: add a new touchscreen calibrator

The new calibrator uses weston_touch_calibration protocol extension and
provides the following features:

- chooses the physical touch device to be calibrated by DEVPATH or by
  the output/head name; device enumeration provided

- the compositor ensures the calibrator window is shown in the correct
  position and size

- no matter how wrong the old calibration is, the touch events will
  always arrive in the application

- the calibration is complete, not incremental; the received touch
  events are guaranteed to be unmodified

- computes a libinput style calibration matrix directly, not the
  WL_CALIBRATION format

- supports multiple touch devices: calibrate one device at a time, and
  show user feedback on touching a wrong device instead of recording bad
  data

- uses four touch point samples: three to compute the calibration, and
  one to verify the calibration is roughly correct

- consistent exit codes

- upload the new calibration into the server after successful
  and verified calibration

Due to using special touchscreen calibration protocol extension, this
application cannot be tested without touch input from the compositor.

Practically all of the above mentioned are unlike how the old
calibrator client worked.

Co-developed by Louis-Francis and Pekka.

v2:
- improve help() text
- rename wrong_touch_handler() to invalid_touch_handler()
- improve debug prints by adding sample number
- reorganize code into sample funcs vs. touch funcs
- add a state machine to properly process touch and related events

Signed-off-by: Louis-Francis Ratté-Boulianne <lfrb@collabora.com>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
v1 Tested-by: Matt Hoosier <matt.hoosier@gmail.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>