Previously, it was assumed that a function argument is either AC or
AC[i], and it was converted to AC or AC+i respectively.  The code is
changed to support any number of dimensions and subscripts, using
array size information from AC's type.  If AC is an array of array
(atomic_uint AC[N][M][R]), the following index calculations are done.

AC          -> AC.arrayIndex
AC[i]       -> AC.arrayIndex + i*M*R
AC[i][j]    -> AC.arrayIndex + i*M*R + j*R
AC[i][j][k] -> AC.arrayIndex + i*M*R + j*R + k

A test is added to exercise these various forms of indexing:

    AtomicCounterBufferTest31.AtomicCounterArrayOfArray

Bug: angleproject:3566
Change-Id: I1e181a7363463d1d0ee4916f35006ed7c58e0f7c
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1739488
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>