Move some GrAuditTrail fuctions to cpp file

TBR=ethannicholas@google.com
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1753753002

Review URL: https://codereview.chromium.org/1753753002
2 files changed