refactor packagegroup-agl-cluster-demo-qtcompositor.bb to make some common pieces

refactor packagegroup-agl-cluster-demo-qtcompositor.bb to make some common pieces

Create the below file in recipes-platform/packagegroups
  packagegroup-agl-networking.bb
  packagegroup-agl-source-han-sans-ttf-fonts.bb
  packagegroup-agl-ttf-fonts.bb
Modify the below bb files to include the new packagegroups
  packagegroup-agl-cluster-demo-platform.bb
  packagegroup-agl-cluster-demo-qtcompositor.bb

Bug-AGL: SPEC-2731

Signed-off-by: Zhou Mingying <zhoumy@cn.fujitsu.com>
Signed-off-by: Liu Wenlong <liuwl.fnst@cn.fujitsu.com>
Change-Id: I422a45ec7d51df2f8621e3297f60383ceb8d69c1
(cherry picked from commit aa6910c87ec4232588593428e98d8903b4c516bf)