Reland "Add inline threshold to SkSL::Program::Settings"

Keep the same default value, but add a (private) API to change it when
compiling SkRuntimeEffect code.

Use the new API to improve fuzzer coverage, by fuzzing with inlining
disabled and (enthusiastically) enabled.

This reverts commit 3e8fae71935893adc69e2b8caee922ec60aa0f59, reworked
to avoid the static initializer.

Change-Id: I7e6cd39d4af2daa4b1be41f1c7d99f32df7a51ab
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/309664
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
6 files changed