extract fibonacci allocator block code

Extract the fibonacci progression block size calculation.
Simplify it by using a common array for the fibonacci number.
Add unit tests to check extreme limits.

Change-Id: I270a713881590f7e17be58dc9072ab7a79a7388d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/345124
Reviewed-by: Ben Wagner <bungeman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Herb Derby <herb@google.com>
3 files changed