[Core] Release PG CPU resources for blocked worker

[jjyao]

Why are these changes needed?

Currently we release CPU resource when a worker process is blocked on ray.get(), however this doesn't work if the CPU resource is inside a PG and this PR fixes it.

Related issue number

Closes #40925

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• Testing Strategy
  • Unit tests
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  • This PR is not tested :(

[rkooo567]

This is theoretically different from previous logics (we called only one of these 2 APIs). Is it guaranteed if allocated_instances is not null lifetime_allocated_instances is null?

[jjyao]

Yup