kuksa-val: Rework to support updated SSL certificates

Changes:
- Tweak the kuksa-val recipe to remove installing a newer server
  certificate (since it will be done elsewhere), and to split the
  certificates up into finer grained packages to ease installing
  them piecemeal and replacing them with other packages.
- Remove the unused genCerts.sh certificate script patch form the
  kuksa-val recipe, an updated patch will be added in the near
  future.
- Added a patch in the kuksa-viss-client recipe that enables the
  library to use certificates installed in /etc/kuksa-certificates or
  /etc/kuksa-val instead of the default ones that are shipped.
- Add kuksa-certificates-agl recipe that installs AGL specific CA,
  server, and client certificates plus the required server and client
  keys to act as a replacement for the default ones shipped with
  KUKSA.val.  The kuksa-certificates-agl name is used to avoid needing
  a rename with a future switch to kuksa-databroker.  Note that the
  RPROVIDES variable is used for the various certificate packages to
  make them installable alternatives to the kuksa-val-certificates-*
  ones.  The certificates installed are valid for 1 year and have
  AGL as the providing organization, longer validity ones will be
  added in follow up commits for Octopus and Pike.
- Update the existing users of kuksa-val-*-certificates with the new
  kuksa-val-certificates-* package names.
- Add PREFERRED_RPROVIDER definitions for the kuksa-val-certificates-*
  packages to quiet the BitBake warnings coming from having multiple
  providers.

Bug-AGL: SPEC-4763

Change-Id: Ic6f1ca8b54f637674cd5ae42df0bed6ca4e729aa
Signed-off-by: Scott Murray <scott.murray@konsulko.com>