Extend getMallocArraySize() to determine the array size if the malloc argument is:

Extend getMallocArraySize() to determine the array size if the malloc argument is:
ArraySize * ElementSize
ElementSize * ArraySize
ArraySize << log2(ElementSize)
ElementSize << log2(ArraySize)

Refactor isArrayMallocHelper and delete isSafeToGetMallocArraySize, so that there is only 1 copy of the malloc array determining logic.
Update users of getMallocArraySize() to not bother calling isArrayMalloc() as well.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85421 91177308-0d34-0410-b5e6-96231b3b80d8