Widget packaging rework

Widget packaging rework

aglwgt.bbclass changes:
- Made the autobuild/agl/autobuild script a hard requirement, as all
  upstream widgets have it, and this is the first step to actually
  using it in the class to drive building the widgets after a
  subsequent round of autobuild script updates.
- Reworked wgt packaging to simplify the logic and split the test,
  debug, and coverage widgets into separate packages to allow
  installing them separately.
- The on target install directories for the widgets have been changed
  to release, test, debug, and coverage under /usr/AGL/apps, with the
  previous logic with respect to the AGLWGT_AUTOINSTALL variable
  being retained for the few widgets that need to go into the
  manualinstall directory. An "autoinstall" symlink has been added to
  point at the release directory to maintain previous behavior.
  This should allow a simple path to configuring installation of the
  debug or coverage widgets on first boot with future changes.
- Added logic to only assume test widgets exist for recipes with
  names starting with "agl-service-". This can be over-ridden by
  defining AGLWGT_HAVE_TESTS as "true" in a recipe.
- Added AGLWGT_EXTRA_BUILD_ARGS variable for passing extra arguments
  to widget builds. Currently its default value includes the previous
  VERBOSE=true that was passed to every autobuild invocation, and
  "${PARALLEL_MAKE}" which has been added to improve build speed.
- Added AGLWGT_PACKAGE_WARN variable to control extra warnings
  around the existence of test/debug/coverage widgets when packaging.
  Once further build rework is done, the default for this will likely
  be changed to "true", currently the output is too verbose to do so.
- Removed over-rides to force building of test widget when building
  with the agl-ptest feature set, as it is now unnecessary and will
  result in an undesired extra copy of the test widget in the release
  folder.

Other changes:
- Created new devel and test packagegroup variants for several of the
  existing packagegroups to contain the associated widgets.
- Added agl-devel-wgt and agl-test-wgt IMAGE_FEATURES to control the
  addition of dbg/coverage and test widgets to images.  Additions to
  the FEATURE_PACKAGES variables have been added in several places to
  add the corresponding widget packagegroups.
- Added the agl-devel-wgt image feature to the agl-devel feature
  template definition to match current behavior.

Bug-AGL: SPEC-3300

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I3a28615db94bbc04e30e98ac3dce8cae942a499f