This is unfortunately a complex test that checks if:

- starting from a empty cluster
- allocating a few instances on it
- serialising it via the Text backend
- loading it back into internal data structures

we end up with the same thing. More precisely, it checks that the
cluster after dump/load is the same as after allocation.

While this is in the Text unittests, as the docstring saying, this
check more stuff than just the dump/load. It increases the overall
coverage by about 3%.

There were a few changes needed for this unittest: adding some Eq
instances for some data types, and fixing a cosmetic bug in
Cluster.iterateAlloc, where the instance indices were growing by 2
instead of by 1 in each round.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>