This CL updates cpplint.py to add some of the c++17 header files to the
list of known c++ headers. We're specifically using optional and variant
in the Tint project and would like to remove the NOLINT lines necessary
to keep the linter happy.

Bug: dawn:1379
Change-Id: I41cacd21e0742f992cdd6913b7f4def556b543c5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3709241
Auto-Submit: Dan Sinclair <dsinclair@chromium.org>
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>