Improve printing of topology information

[Keno]

Currently we say things like "<8 TPU chips in 2x2x2 topology>", which is informative, but doesn't match Google terminology. We could try printing something like "<TPUv3-8 in 2x2 topology>". We don't get the chip kind information from the topology, but we could for now just determine it from the memory information.

[Keno]

Turns out the memory information does not reflect the actual TPU memory, so we're gonna have to figure out something else here. It is possible to get this from the profiler, but that's on a separate port, so it's a bit annoying.