Improvements to verify --reduce #15508

Job	Run time
Check if image exists in registry	6s
licensing	2m 47s
cancel	3s
pyflakes	5m 12s
linux (ubuntu-20.04, debug)	23m 32s
linux (ubuntu-20.04, release)	1h 31m 55s
linux (ubuntu-20.04, codecov)	6m 15s
linux-fpga (ubuntu-20.04, debug)	27m 17s
Build image	0s
Build SLES image	0s
format	2m 52s
tidy	2m 21s
cppcheck	2m 0s
sles	1m 52s
	2h 46m 12s

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