Move ProgramImpl definitions into Processor subclass headers.

Move ProgramImpl function definitions into Processor subclass cpp files.

Delete separate h/cpp files.

Modify GrGLSLVaryingHandler::addPassThroughAttribute to break #include
cycle. It now takes a ShaderVar rather than a GP::Attribute, making
it slightly more flexible as the input can be any variable defined
in the vertex shader.

Bug: skia:11358
Change-Id: I94ee8cd44d29e194216592ecae5fd28de785c975
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/438596
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
85 files changed