[gitsync] Add creation script for internal service account
[gitsync] Add creation script for internal service account

Bug: skia:8636
Change-Id: I499eea7e1afe0556d251e883ee267b463d9fb02c
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/202781
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Reviewed-by: Stephan Altmueller <43343ec95731c0e8daa7359daf7f2f3935582b24@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot