Rename smart->small in MM apis

Rename smart->small in MM apis

Summary: Within the scope of the MemoryManager, the term "smart" generally referred
to the size-segregated freelists used for small object allocations. Rename
things accordingly:

size-tracked allocation apis:
  smartMallocSize      mallocSmallSize
  smartMallocSizeSlow  mallocSmallSizeSlow
  smartMallocSizeBig   mallocBigSize
  smartFreeSize        freeSmallSize
  smartFreeSizeBig     freeBigSize

malloc-style support (for req::malloc)
  smartMalloc          malloc
  smartMallocBig       mallocBig
  smartFree            free
  smartRealloc         realloc
  smartCallocBig       callocBig

constants:
  kMaxSmartSize              kMaxSmallSize
  kSmartFreeFill             kSmallFreeFill
  kSmartFreeWord             kSmallFreeWord
  kSmartSizeAlign            kSmallSizeAlign
  kSmartSizeAlignMask        kSmallSizeAlignMask
  kLgSmartSizeQuantum        kLgSmallSizeQuantum
  kNumSmartSizes             kNumSmallSizes
  kMaxSmartSizeLookup        kMaxSmallSizeLookup
  kSmartPreallocCountLimit   kSmallPreallocCountLimit
  kSmartPreallocBytesLimit   kSmallPreallocBytesLimit

utilites:
  smartSizeClass          smallSizeClass
  smartSize2IndexCompute  computeSmallSize2Index
  smartSize2IndexLookup   lookupSmallSize2Index
  smartIndex2Size         smallIndex2Size
  SMART_SIZE{S}           SMALL_SIZE{S}
  estimateSmartCap        estimateCap

Reviewed By: @jasone, @markw65

Differential Revision: D2223217