SkSL description methods are now only present in debug mode

As they are a significant chunk of code, this reduces the size of the
release executable.

Change-Id: Ib764b3ec6244629e50941b0101a540e49d56c320
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/261955
Reviewed-by: Greg Daniel <egdaniel@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
66 files changed