Add SkSLTypeShared cpp file.

Previously, the code for converting an SkSLType to a string only
existed in Ganesh, in GrGLSL.cpp/.h. This has now been moved to
SkSLTypeShared.cpp, and the Ganesh file was removed entirely.

Now that a cpp exists, I also moved some rarely-used utility function
bodies out of the header.

Change-Id: Id37ac54dabfe8b1264a2662a00c9780a1ecae2ba
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/556602
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
17 files changed