SkMetaData: move from src/ to tools/

Change-Id: If581c8ceeaa76985535cb7b6772742f0011cfe8e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/227436
Commit-Queue: Hal Canary <halcanary@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
Auto-Submit: Hal Canary <halcanary@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
7 files changed