Add `dumpTreeInfo` debug method to GrFragmentProcessor.

This is a net reduction in code size because this idea was already
implemented separately in two places:
- dump_fragment_processor_tree (GrProcessorSet)
- describe_fp (ProcessorTest)

This consolidates the implementations. This CL also fixes a handful of
dumpInfo() methods that were not sufficiently descriptive--e.g. the FP
name was missing, or the implementation was just buggy.

Change-Id: If34ac46c97e9ae431c7c64b1247fc619703580b2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/309324
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
8 files changed