Reverse dependency between SkScalar.h and SkFixed.h. The following are unused in Chromium, Android, Mozilla, and Google3: - SkFixedToScalar - SkScalarToFixed The following are additionally unused in Skia: - SkStrAppendFixed - SkWriteBuffer::writeFixed BUG=skia: GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1841123002 Review URL: https://codereview.chromium.org/1841123002