Begin switch to SkFontStyle for legacy calls.

Begin switch to SkFontStyle for legacy calls.

This adds SK_VERY_LEGACY_CREATE_TYPEFACE which, when defined, provides
only the old interface.

Ideally, everyone would switch directly to SkFontMgr and use one of the
newer calls, but there is currently no path for current users to get
there. This updates all the internals to use SkFontStyle, after
switching these over the higher level APIs can be switched.

The Chromium follow on patch can be seen at https://crrev.com/1877673002

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1873923002

TBR=reed
This doesn't really change API, just modernizes it.

Review URL: https://codereview.chromium.org/1873923002