juno: remove juno boot tests from CI+1

Considering the number of CI false positive failures caused by lava
its better to remove all Juno boot tests from CI+1 jobs and keep
it only in CI+2 or main.
Following changes are done:
 - Remove all Juno boot tests from CI+1
 - Keep all juno-l1 boot tests to Linux shell boot in CI+2
 - Create a new group in tf-main for all juno boot tests

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I3b02c1523f0ef96f3179030c91ba7860ccb1fc85
4 files changed