meta-agl-core: Revise weston-ini-conf mechanism

meta-agl-core: Revise weston-ini-conf mechanism

The recent layer reorganization broke the landscape vs portrait scheme
based on bbappend'ing the weston-ini-conf recipe in the previous cluster
and html5 demo layers.  To fix this and to facilitate being able to
easily build the mix of demo platform images, the weston.ini generation
mechanism in the weston-ini-conf has been revised to build multiple
packages.

Instead of relying on SRC_URI to install weston.ini fragments into
WORKDIR and grabbing all of them with a *.cfg glob, an explicit list
built from new WESTON_FRAGMENTS and WESTON_DISPLAYS variables is used.
The fragments listed in WESTON_FRAGMENTS are used to generate both
weston-ini-conf and weston-ini-conf-landscape packages containing
uniquely named files (weston.ini.default and weston.ini.landscape,
respectively), and the OE update-alternatives mechanism is used to have
weston.ini point at the appropriate file on installation.  For now, the
two packages are explicitly marked as incompatible with one another,
but this could be tweaked in the future if switching between them on
target is desired.

Additional notes:
- A RPROVIDES of "weston-ini" has been defined for the weston-ini-conf
  packages and a RDEPENDS on it added to weston-init.  This should
  allow members to drop in a complete alternative solution while still
  having a dependency chain.
- The various meta-agl-bsp bbappends of weston-ini-conf have for the
  most part been updated to yield the same behavior as before, though
  with an eye towards using machine overrides to ease multiconfig usage
  down the road.  This includes the currently unused Raspberry Pi
  touchscreen support, which has been left since it may still see use.
- An exception to the above, however, is that the support for the
  touchscreen on the dra7 EVM has been removed, as upstream dropped the
  support for the screen on the available test hardware and at present
  it only seems feasible to support external HDMI monitors.
- The unused fbdev fragment used to support meta-freescale in the past
  has been removed.
- The virtual and virtual-landscape fragments have been renamed to
  virtual-270 and virtual-0 to better indicate the orientation and match
  the naming used for the other fragments.  It is likely that future
  work will need to split the display enabling and orientation aspects,
  as the current tying together of the two results in configurations
  somewhat overly specific to the actual AGL demo systems.

Bug-AGL: SPEC-3745

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I2a968781182a346c1d483cca4fd7337679e58118
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/25860
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-boot-test: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>