ktest.pl: Add new PATCHCHECK_SKIP option to skip testing individual commits

When testing a series of commits that also includes changes to the Linux
tools directory, it is useless to test the changes in tools as they may
not affect the kernel itself. Doing tests on the kernel for changes that
do not affect the kernel is a waste of time.

Add a PATCHCHECK_SKIP that takes a series of shas that will be skipped
while doing the individual commit tests.

For example, the runtime verification may have a series of commits like:

$ git log --abbrev-commit --pretty=oneline fac54932~1..HEAD
3d3800b4 rv: Remove rv_reactor's reference counter
3d3c3761 rv: Merge struct rv_reactor_def into struct rv_reactor
24cbfe18 rv: Merge struct rv_monitor_def into struct rv_monitor
b0c08dd5 rv: Remove unused field in struct rv_monitor_def
58d5f0d4 (debiantesting-x86-64/trace/rv/core) rv: Return init error when registering monitors
560473f2 verification/rvgen: Organise Kconfig entries for nested monitors
9efcf590 tools/dot2c: Fix generated files going over 100 column limit
1160ccaf tools/rv: Stop gracefully also on SIGTERM
f60227f3 tools/rv: Do not skip idle in trace
f3735df6 verification/rvgen: Do not generate unused variables
6fb37c2a verification/rvgen: Generate each variable definition only once
8cfcf9b0 verification/rvgen: Support the 'next' operator
fac54932 rv: Allow to configure the number of per-task monitor

Where the first commit touches the kernel followed by a series of commits
that do not, and ends with commits that do. Instead of having to add
multiple patchcheck tests to handle the gaps, just include the commits
that should not be tested:

$ git log --abbrev-commit --pretty=oneline fac54932~1..HEAD |
  grep -e verification -e tools/ | cut -d' ' -f1 |
  while read a ; do echo -n "$a "; done
560473f2 9efcf590 1160ccaf f60227f3 f3735df6 6fb37c2a 8cfcf9b0

Then set PATCHCHECK_SKIP to that, and those commits will be skipped.

 PATCHCHECK_SKIP = 560473f2 9efcf590 1160ccaf f60227f3 f3735df6 6fb37c2a 8cfcf9b0

Cc: John 'Warthog9' Hawley <warthog9@kernel.org>
Cc: Dhaval Giani <dhaval.giani@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/20250725112153.1dd06b84@gandalf.local.home


Signed-off-by: Steven Rostedt <rostedt@goodmis.org>