ci: enable LAVA boot and smoke tests on qemu devices for new MRs

Given test scope for new MRs is not defined yet and we only have one rpi4, b68 and c61 in the warsaw lab which are occupied mostly by daily scheduled pipeline, starting with boot and smoke tests on qemu devices is a good starting point for per MR testing.

.lava-test-scheduled extends .lava-test and is scheduled pipeline only. Long run jobs like ltp should extends the .lava-test-scheduled. Jobs that extend .lava-test will be added to MR's pipeline and scheduled pipeline.

Solves #486 (closed).

Signed-off-by: Chase Qi chase.qi@linaro.org