feat(framework) Add flwr log

[chongshenng]

Issue

Description

With the SuperExec service, the ServerApp logs are not easily accessible. This CLI enables a request to be sent to the service.

Related issues/PRs

The companion PR below adds log capturing to the SuperExec service. This PR can be merged independently of it.

• feat(framework) Add SuperExec logcatcher #3584

Blocks:

• feat(framework) Add log functions to flwr log #3611
• feat(framework) Add logstream functionality to flwr run #3613

Proposal

Explanation

flwr log sends a requests to the SuperExec service to get the log stream and receives a response from it. The response will be handled in two ways:

1. Run flwr log <RUN_ID> <DIRECTORY> <FEDERATION_NAME>. The default is stream=True (--stream). This streams the logs and periodically refreshes the gRPC connection.
2. Run flwr log <RUN_ID> <DIRECTORY> <FEDERATION_NAME> --show. This prints the logs and closes the connection gracefully. Every subsequent execution of this command always prints the logs from the beginning of the run.

Checklist

• Implement proposed change
• Make CI checks pass
• Ping maintainers on Slack (channel #contributions)

Any other comments?

[chongshenng]

@jafermarq About your comments here, we need to refactor flwr log and flwr run together soon since they share a lot of similar code. It's substantial work worthy of another PR.