[LAA] Add a test case to show incorrect dependency classification (NFC). (#70473)

Currently the loop access analysis classifies this loop as unsafe to
vectorize because the memory dependencies are
'ForwardButPreventsForwarding'. However, the access pattern is
'write-after-read' with no subsequent read accessing the written memory
locations. I can't see how store-to-load forwarding is applicable here.

void vectorizable_Read_Write(int *A) {
  for (unsigned i = 1022; i >= 0; i--)
    A[i+1] = A[i] + 1;
}