meta-agl-profile-core: Add support for running gcovr on target

meta-agl-profile-core: Add support for running gcovr on target

Changes:
- Add recipe for gcovr gcov-based coverage report generating tool.
- Add bbappend to apply patch to gcovr to add a new command-line
  option that allows working with the coverage information from the
  AGL widgets on target.  The goal is to get this change upstream,
  hence not having it in the recipe (which also will be sent for
  inclusion in meta-oe).
- Add a recipe to install an included wrapper script for gcovr
  (unsurprisingly named "gcovr-wrapper") that enables running it
  against bindings on target.  The script supports installing the
  coverage version of a binding and running pyagl tests, afm-test
  test widget, or a user-supplied command before running gcovr in a
  carefully crafted environment that will allow it to work without
  impacting the root filesystem of the target.
- Add gcov-symlinks, gcovr, and gcovr-wrapper to the
  packagegroup-agl-core-devel package group so they will be
  available in agl-devel images.  The gcov-symlinks package adds
  /usr/bin/gcov, which simplifies picking it up for gcovr.

Bug-AGL: SPEC-3589

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: Ia2fdc200e4e0683f93a6e2a863311cd2107c962b
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/25337
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>