Test support of v5litepod-8

[IrvingMg]

Follow-up of #292 to test support TPU v5litepod-8 once the resources for testing become available.

[gcie]

I think the value of chips_per_vm for v5litepod-8 (line 1159 below) is invalid in the configuration (should be 4). This TPU has 8 chips total, not per vm.

https://github.com/AI-Hypercomputer/xpk/blob/ec9e9d4b19241e0a62d81c70cf3ca5b4295375fb/src/xpk/core/system_characteristics.py#L1154-L1162

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