feat(publisher): add fileserver worker

[wuhuizuo]

upload to KS3 buckect.

Signed-off-by: wuhuizuo [email protected]

[ti-chi-bot]

I have already done a preliminary review for you, and I hope to help you do a better job.

Summary:
The pull request adds a new fileserver worker to upload to the KS3 bucket. It also renames the worker-example.yaml file to worker-example.tiup.yaml and adds a new worker-example.fileserver.yaml file.

Potential problems:

1. The initTiupWorkerFromConfig function has only 2 return values but the return statement in the function has 3 values, which may cause a compilation error.
2. In the NewFsWorker function, the defaultMaxKS3Retries constant is defined but not used.
3. In the NewFsWorker function, the LogLevel of s3Client is set only when the logger's level is lower than or equal to DebugLevel, which may cause the log level to be inconsistent.

Fixing suggestions:

1. Remove the error return value from the initTiupWorkerFromConfig function's return statement since the error is already logged and the function can return nil.
2. Use the defaultMaxKS3Retries constant in the NewFsWorker function to set the MaxRetries of s3Client.
3. Set the LogLevel of s3Client unconditionally in the NewFsWorker function.

Overall, the changes look good but it would be helpful to have more context on why the fileserver worker was added and how it will be used.

[wuhuizuo]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: wuhuizuo

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