[improve][fn] Avoid gRPC timeout when getting status of a dead process runtime

[Dream95]

Motivation

In process runtime mode, When the child process had exited, the stub could still be non-null, so the call continued through gRPC getFunctionStatus and could block until the 5-second deadline expired.

Aligned ProcessRuntime.getFunctionStatus() with ThreadRuntime.getFunctionStatus() by checking !isAlive() before invoking gRPC.

Modifications

• In ProcessRuntime.getFunctionStatus(), if !isAlive(), complete immediately with running=false and populate failureException from the stored deathException when available, without invoking gRPC.

Verifying this change

• Make sure that the change passes the CI checks.

Does this pull request potentially affect one of the following parts:

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

[lhotari]

LGTM