[HUDI-2770] - Docs for (HUDI-2737) - Use earliest instant for async compaction and clustering

[kywe665]

What is the purpose of the pull request

In PR: #3991, the --instant-time is no longer required for Hudi compaction and clustering utilities. As I made the simple change for this I also discovered that the compaction docs were unclear on how to schedule and then separately execute compaction asynchronously.

Brief change log

• Added note about --instant-time no longer being required in clustering.md
• Added note about --instant-time no longer being required in compaction.md
• Reworded and expanded compaction doc to make scheduling vs execution clear

Verify this pull request

This pull request is doc changes only.

Committer checklist

• [ X] Has a corresponding JIRA in PR title & commit

• [X ] Commit message is descriptive of the change

• [ X] CI is green

• [X ] Necessary doc changes done or have another open PR

• [ X] For large changes, please consider breaking it into sub-tasks under an umbrella JIRA.

[kywe665]

@yihua take a look to see if this covers your updates in PR: #3991

[yihua]

LGTM overall. Improved clarity. I only have a few minor comments.

[yihua]

👍 I'll let @bhasudha take another pass.

[bhasudha]

Thanks @kywe665 Left some comments. Please let me know if you need clarification on them.

[kywe665]

Thanks @bhasudha, I made the corresponding updates

[bhasudha]

LGTM. Thanks @kywe665

[bhasudha]

@kywe665 do you want to rephrase the commit message to avoid commit msg from all of the individual commit messages that includes feedback and reviews ? I think we can then merge this one.