Refactor: Remove @LegacyFileIO and Make DelegationRefreshToken use new cluster.yaml

[HotSushi]

Summary

Let's start refactoring the old code out 🙌

There are two refactors:

1. Remove old FileIO instance provisioned via FsStorageProvider

// old code
public class MainApplicationConfig
  @Bean
  public FileIO provideIcebergFileIO() {
         return new HadoopFileIO(fsStorageProvider.storageClient().getConf())
  }

2. DelegationTokenRefresher should use the new cluster.yaml

 // new cluster yaml
storages:
  default-type: "hdfs"
  types:
     hdfs:
        rootpath: "/tmp/unittest"
        endpoint: "hdfs://localhost:9000"
        parameters:
           token.refresh.enabled: "true"             <----------- THIS
           token.refresh.schedule.cron: "* * * * * ?"          <----------- THIS

There are no major changes to code otherwise.

Changes

• Refactoring
• Tests

Testing Done

✅ Added unit tests for token refresh that were missing before 🥳
✅ mint build and existing tests pass
✅ manually tested token refresh code in docker setup
✅ manually tested fileIO code in docker setup

[HotSushi]

cc: @ctrezzo

[autumnust]

Is there coordination required when picking up this change internally, since you are making some config changes ?

[abhisheknath2011]

LGTM

[autumnust]

thanks for answering the questions. lgtm