[IcebergIO] cleanups, improvements, and test tweaks

[ahmedabu98]

Collection of some improvements:

• cache Catalog instead of recreating it unnecessarily
• use faster IO implementation org.apache.iceberg.gcp.gcs.GCSFileIO in tests
• tests drop tables and namespaces right after completion
• tests close resources properly

[github-actions]

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[github-actions]

Reminder, please take a look at this pr: @damondouglas @damccorm @shunping

[damondouglas]

@ahmedabu98 LGTM

[shunping]

LGTM

[ahmedabu98]

Failing test is unrelated:

> Task :runners:google-cloud-dataflow-java:worker:test

org.apache.beam.runners.dataflow.worker.windmill.client.grpc.GrpcDirectGetWorkStreamTest > testConsumedWorkItems_itemsSplitAcrossResponses FAILED
    org.junit.runners.model.TestTimedOutException at GrpcDirectGetWorkStreamTest.java:130