Use SkBitmapProcStateAutoMapper for filter samplers also

Observation: filter procs are also biased by s.fFilterOne{X,Y} / 2.  They all do
something along these lines:

  s.fInvProc(s.fInvMatrix,
    SkIntToScalar(x) + SK_ScalarHalf,
    SkIntToScalar(y) + SK_ScalarHalf, &srcPt);

  SkFixed fx = SkScalarToFixed(srcPt.fX) - (s.fFilterOneX >> 1);
  SkFixed fy = SkScalarToFixed(srcPt.fY) - (s.fFilterOneX >> 1);

It's trivial to extend SkBitmapProcStateAutoMapper to handle this internally, and
convert everyone off explicit mapping.

R=reed@google.com
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Review URL: https://codereview.chromium.org/1661613002
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