free -> reset

The C++ standard library uses ".reset()" where we sometimes write ".free()".
We also use ".reset()" quite a lot.  This standardizes on ".reset()".

This is one more step towards dropping SkAutoTDelete in favor of the standard
std::unique_ptr.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1811723002

Committed: https://skia.googlesource.com/skia/+/0e3738db89e86035ed5d4f629bf58b817b1e5274

Review URL: https://codereview.chromium.org/1811723002
16 files changed