remove upper limit on number of pipeline stages

Bicubic is going to blow right past 48.  At this point the fixed preallocation strategy is starting to look naive... at 64 we'd allocate just over 1K for every pipeline (and every compiled pipeline). 

CQ_INCLUDE_TRYBOTS=skia.primary:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD

Change-Id: Ib2944ead1217123aba2b6347fd9d5315217540c9
Reviewed-on: https://skia-review.googlesource.com/5551
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
3 files changed