[Feature] [TPU host offload] sglang bench_serving tool example

[saikat-royc]

Description

Start with a short description of what the PR does and how this is a change from
the past.

1. Benchmark pod spec to deploy sglang bench_serving.py
2. two workload pod specs, to serve llama-3.3-70B. deploy-baseline.yaml does not have any TPU connector enabled, the deploy-host-offload.yaml has the tpu local connector enabled.
3. README.md captures steps to run the benchmark in GKE

The rest of the description includes relevant details and context, examples:

• why is this change being made,

This tool will help us evaluate the perf of tpu local connector against baseline for various prefix cache scenarios and fix any bottlenecks and bugs

• the problem being solved and any relevant context,
• why this is a good solution,
• some information about the specific implementation,
• shortcomings of the solution and possible future improvements.

If the change fixes a bug or a Github issue, please include a link, e.g.,:
FIXES: b/123456
FIXES: #123456

Tests

Please describe how you tested this change, and include any instructions and/or
commands to reproduce.

Checklist

Before submitting this PR, please make sure:

• I have performed a self-review of my code.
• I have necessary comments in my code, particularly in hard-to-understand areas.
• I have made or will make corresponding changes to any relevant documentation.