This allows people to pin a specific version of pylint when running
it.  The default behavior is unchanged: we run pylint-1.5.6 still
as we've created a vpython wheel in cipd for it.  But for projects
that want to move to a newer version, they can pick any of the new
1.x wrappers.  Having the full set of versions here allows projects
to incrementally move to newer versions as the lint delta between
1.5 & 1.6 tends to be much smaller than 1.5 & 1.9.

We don't include support for the newer 2.x series as those only
support Python 3 which the codebase isn't ready for.

Bug: 866772
Test: `./pylint ...` still works & shows pylint-1.5
Test: `./pylint-1.5 ...` runs the v1.5 version
Test: `./pylint-1.8 ...` runs the v1.8 version
Change-Id: I7c47187493564db81e3eb28c6dbd09e6309ead46
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1752507Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>