[opt](variant) add serialized sparse column

[csun5285]

What problem does this PR solve?

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

Release note

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Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:
    • This is a refactor/code format and no logic has been changed.
    • Previous test can cover this change.
    • No code files have been changed.
    • Other reason

• Behavior changed:

  • No.
  • Yes.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

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[github-actions]

clang-tidy made some suggestions

[github-actions]

warning: method 'insert_from_sparse_column_and_fill_remaing_dense_column' can be made const [readability-make-member-function-const]

be/src/vec/columns/column_object.cpp:1156:

-         size_t start, size_t length) {
+         size_t start, size_t length) const {

[github-actions]

warning: redundant return statement at the end of a function with a void return type [readability-redundant-control-flow]

Suggested change

	return;
	}
	}

[eldenmoon]

LGTM