releasetools: Dump mkfs/fsck/simg2img outputs on error.

The output (stdout and stderr combined) would be helpful in understanding
the cause of the failure.

Not changing other occurrences in build_image.py yet, since it's less
obvious if a failed call should be considered fatal (thus whether to
dump such outputs). For example, GetVeritySize() simply returns 0 on
failed calls. They deserve further clean-ups in later CLs (with unit
tests).

Bug: 71864688
Test: Inject errors into mke2fs/e2fsck/simg2img. `m snod` prints outputs.
Test: `m snod` remains quiet on successful runs.
Change-Id: I172403f6cd05bce93767265dbcb110271a68e2a8