test.py imports deps/v8/tools/utils.py but that file is gone after the
upgrade to 3.18.4 in commit 2f75785. Resurrect the file in tools/

Adding --flaky-tests option, to allow regarding flaky tests failures
as non-fatal.

Currently only observed by the TapProgressIndicator, which will
add a # TODO directive to tests classified as flaky. According to the
TAP specification, the test harness is supposed to treat failures
that have a # TODO directive as non-fatal.

This is a minimal effort to support test output written both to
stdout and file in order to get our buildbots understanding
test output.

Cherry picked from jbergstroem/node@3194073
Original commit message follows:
  PR-URL: nodejs/node#934
  Reviewed-By: Chris Dickinson <[email protected]>
  Reviewed-By: Ben Noordhuis <[email protected]>

Conflicts:
	tools/test.py

Conflicts:
	tools/test.py

On a few of our installations (namely CentOS), passing 'INFO'
resulted in a silent loglevel. Use a logging constant instead.

Cherry-picked from nodejs/node@8606793
Original commit metadata follows:
  Fixes: nodejs/build#104
  PR-URL: nodejs/node#1842
  Reviewed-By: Rod Vagg <[email protected]>

Adding support for specifying flaky test mode to
the test runner:
- via an environment variable FLAKY_TESTS for Makefile
- via an argument ignore-flaky for vcbuild.bat

Make the test runner return a 0 exit code when only
flaky tests fail and --flaky-tests=dontcare is specified.

Adding a single rule to be called from Jenkins.