[HUDI-4478] Rename existing Spark/Flink modules concisely

[CTTY]

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[CTTY]

As discussed in #5943 , we should have a more concise naming pattern for Spark/Flink modules

[yihua]

@CTTY Let's target this for the next release, not merging into master for 0.12.0. wdyt? cc @codope @xushiyan @alexeykudinkin @danny0405

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CI report:

• 18944f9 Azure: FAILURE

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[alexeykudinkin]

@CTTY can you please summarize the changes in the description?

[yihua]

@alexeykudinkin Do you think we still need part of the changes from this PR, given #6550?

[alexeykudinkin]

@yihua we do, i see this PR contains actually some other changes besides just renaming the modules. We should follow-up on it after #6550 lands though (since it deduplicates many of the classes, meaning that we don't need to move these)

[nsivabalan]

@alexeykudinkin @CTTY : can you guys align on how to make progress on this patch. as of now, have marked it as WIP label. please remove once we have alignment and its ready to be reviewed again.

[yihua]

We have made significant changes in Spark and Flink integration since this PR is created. Closing this one. Feel free to create a new PR on the latest master if the changes are still useful.