[refine](column) enforce nullable nested types for array (#63088)

[Mryange]

This PR makes the nested types inside Array explicitly nullable in BE type implementations, instead of relying on implicit caller-side conventions.

DataTypeArray now always stores nullable nested element type DataTypeArraySerDe updated to follow the same invariant

#63088

What problem does this PR solve?

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

Release note

None

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

[hello-stephen]

Thank you for your contribution to Apache Doris.
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Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[Mryange]

run buildall

[hello-stephen]

FE UT Coverage Report

Increment line coverage 73.68% (14/19) 🎉
Increment coverage report
Complete coverage report

[hello-stephen]

FE Regression Coverage Report

Increment line coverage 100.00% (19/19) 🎉
Increment coverage report
Complete coverage report

[hello-stephen]

BE Regression && UT Coverage Report

Increment line coverage 95.83% (23/24) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	73.83% (27479/37221)
Line Coverage	57.49% (297906/518230)
Region Coverage	55.14% (250139/453673)
Branch Coverage	56.53% (108282/191540)

[Mryange]

run cloud_p0

[hello-stephen]

BE Regression && UT Coverage Report

Increment line coverage 95.83% (23/24) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	73.83% (27479/37221)
Line Coverage	57.49% (297906/518230)
Region Coverage	55.14% (250139/453673)
Branch Coverage	56.53% (108282/191540)

[hello-stephen]

FE Regression Coverage Report

Increment line coverage 100.00% (19/19) 🎉
Increment coverage report
Complete coverage report