streamline SkVM test rebaselining

  - keep expectations in resources/
  - overwrite automatically if needed
    so we can see the diff in Git

Change-Id: I2486b127ebcc7f40332fd0462e38b1af04d3e32b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/218038
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
2 files changed