Convert DstTexture to DstProxy (take 2)

The last GrTexture-based TextureSampler::reset call must be removed before the TextureSamplers can become purely GrTextureProxy-backed

Reland of: https://skia-review.googlesource.com/c/16908/ (Convert DstTexture to DstProxy)

Split out of: https://skia-review.googlesource.com/c/10484/ (Omnibus: Push instantiation of GrTextures later (post TextureSampler))

Change-Id: I3a497b6a950fad899f23882c0a9552894ef640f8
Reviewed-on: https://skia-review.googlesource.com/17205
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
22 files changed