A long chain of fir.pack_arrays might require multiple iterations
of the greedy rewriter, if we use down-top traversal. The rewriter
may not converge in 10 (default) iterations. It is not an error,
but it was reported as such.

This patch changes the traversal to top-down and also disabled
the hard error, if the rewriter does not converge soon enough.

This patch allows optimizing redundant array repacking, when
the source array is statically known to be contiguous.
This is part of the implementation plan for the array repacking
feature, though, it does not affect any real life use case
as long as FIR inlining is not a thing. I experimented with
simple cases of FIR inling using `-inline-all`, and I recorded
these cases in optimize-array-repacking.fir tests.