We had output dependent on complex_continue being set, but setting that
flag was dependent on unordered_set declaration order. Make it invariant
to ordering and change the implementation so it knows about the new
temporary hoisting for access chains.
This avoids a lot of huge code changes.
Arrays generally cannot be copied in and out of buffers, at least no
compiler frontend seems to do it.
Also avoids a lot of issues surrounding packed vectors and matrices.