ci: Split build jobs based on target platform

Pipeline matrices are divided based on the targets
to decrease the number of build jobs needed for `test-applications`
job as they would exceed the limit (50 jobs) after adding
support for software inference with speech-recognition application
for all platforms, the limitation of 50 jobs comes from `needs`
keyword used in `test-applications` job.

Signed-off-by: Ahmed Ismail <Ahmed.Ismail@arm.com>