ci: run Zephyr builds in parallel #807

Job	Run time
Prepare build environment	3m 51s
Build loader for nano33ble	1m 19s
Build loader for giga	1m 46s
Build loader for unoq	1m 15s
Build loader for opta	1m 32s
Build loader for portentac33	1m 7s
Build loader for niclasense	1m 8s
Build loader for ek_ra8d1	1m 42s
Build loader for frdm_rw612	1m 11s
Build loader for portentah7	1m 31s
Build loader for frdm_mcxn947	2m 12s
Package zephyr_main	57s
Package zephyr_unoq	21s
Package zephyr	1m 8s
Package zephyr_contrib	32s
Clean up intermediates	5s
Test zephyr_main:giga	2m 39s
Test zephyr_contrib:ek_ra8d1	2m 32s
Test zephyr_main:opta	2m 26s
Test zephyr_main:nano33ble	2m 31s
Test zephyr_main:portentac33	2m 30s
Test zephyr_main:niclasense	2m 36s
Test zephyr:unoq	2m 22s
Test zephyr_main:portentah7	2m 31s
Test zephyr_contrib:frdm_mcxn947	1m 43s
Test zephyr_contrib:frdm_rw612	1m 53s
Collect logs	6s
Publish core	0s
verify-core	0s
Prepare jsons	18s
	45m 44s

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