Removing fOffsets array from Run; optimizing copyTo

Change-Id: I4df661f800436ddb2b2bdb0cf19017e651332971
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/295236
Commit-Queue: Julia Lavrova <jlavrova@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
Reviewed-by: Mike Reed <reed@google.com>
6 files changed