Search for expected keywords in the output of cbfstool tests and not a...

Search for expected keywords in the output of cbfstool tests and not a specific output. (Closes: !42)

Stop trying to track every small change in the output of the "cbfstool print"
command, just search for some expected keywords instead.

- Around 2015 the legacy master header stopped being generated by default:
   https://www.coreboot.org/CBFS#FMAP
   https://review.coreboot.org/c/coreboot/+/10135



- In v4.7, cbfstool added the Comp(ression) column.

- v4.8 or v4.9 added a new header " FMAP REGION: COREBOOT", see new
  contextual diff below.

Signed-off-by: Chris Lamb <lamby@debian.org>