meta-app-framework: Update app template scheme

meta-app-framework: Update app template scheme

Changes to support the move to systemd unit based app enumeration in
applaunchd:
- Bump applaunchd SRCREV to pick up enumeration changes.
- Tweak the polkit rule to match agl-app* instead of agl-app@*
  to allow more flexibility with respect to different app templates.
- Tweak the Description field definition in the agl-app service
  template to just use the instance name, as that field is now used
  for the application display name by applaunchd.
- Add a agl-app-web service template for web apps.
- Add a agl-app.bbclass for use in application recipes to simplify
  installation of the now required systemd template instances and
  potential generation of override files to tweak application
  configuration.
- Split the agl-app and agl-app-web templates into their own packages
  in the applaunchd recipe so they can be depended on by applications
  as required.
- Move applaunchd installed systemd units and override files to
  /lib/systemd/system since that matches the upstream recommendation
  for units installed as part of the system installation.

Bug-AGL: SPEC-4466

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I32ff6c9624850662856b79a2b14b33a05e7f9a65
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/27835
Tested-by: Jenkins Job builder account
ci-image-build: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account
Reviewed-by: Jose Dapena Paz <jdapena@igalia.com>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>