[Feature] Support config max length of zone map index

[HappenLee]

Proposed changes

Like postgresql's Brin index, by default, records 128 rows of data once. The current Doris default page size is 64k, so a reasonable zonemap index length set 512byte.

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
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• Code refactor (Modify the code structure, format the code, etc...)
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Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I have created an issue on (Fix [Proposal] Support large variable-length string type #6276) and described the bug/feature there in detail
• Compiling and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• If these changes need document changes, I have updated the document
• Any dependent changes have been merged

[morningman]

Do we need to change the compare method of zonemap index?

[morningman]

LGTM

[github-actions]

PR approved by at least one committer and no changes requested.

[github-actions]

PR approved by anyone and no changes requested.