[refactor](be) Encapsulate cached constant columns

[Mryange]

What problem does this PR solve?

Cached constant expressions could expose either a ColumnConst or a single-row data column, forcing callers to inspect the physical column type. This change makes ColumnPtrWrapper store a private, single-row data column, unwraps ColumnConst without copying, and creates ColumnConst only when broadcasting the cached value. It also removes redundant constant evaluation from VMatchPredicate::open().

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]

/review

[github-actions]

Request changes: the production refactor is sound, but the test-contract migration is incomplete and normal BE-UT configurations cannot pass as submitted.

Critical checkpoint conclusions:

• Goal and proof: Centralizing the cached single-row data column removes caller-side physical-shape checks and preserves production behavior, but the changed/new tests do not prove a passing cross-build contract; two blocking test failures are called out inline.
• Scope and clarity: The change is conceptually focused. The accessor migration covers all repository consumers; the related VMatchPredicate removal was verified as a no-op for valid plans because MATCH retains a nonconstant slot child.
• Concurrency: The wrapper is immutable after construction and existing shared pointers are populated during expression open. No new thread, lock, atomic, dependency-order, or deadlock behavior was introduced; valid scan constant-false paths still signal readiness as before.
• Lifecycle, memory, and nullability: The wrapper owns the unwrapped ColumnPtr; FunctionContext clones share that ownership, so cached StringRef values remain live. Nullable and array/map/struct row-zero semantics and COW ownership are preserved, with no new untracked allocation or reference cycle.
• Configuration and compatibility: No configuration, FE-BE variable, serialization, storage-format, or rolling-upgrade contract changes. The internal source API migration is complete across the repository.
• Parallel paths and special checks: File, mock, OLAP, generic scan, scalar-function, collection-IN, constant rebroadcast, and ANN paths were traced. The one-row check is a valid production invariant, but its direct test/mock callers and build-mode-specific failure behavior were not fully migrated.
• Test coverage and results: Existing scan-normalization cases now fail during setup, and the new unconditional death test fails under NDEBUG. The visible macOS BE check is compile-only with MAKE_TEST=OFF, so it does not cover either issue. No local builds or tests were run because this review runner prohibits builds.
• Observability: No new runtime path requires logs, metrics, or tracing.
• Transactions, persistence, and writes: Not applicable; the PR changes neither transaction state nor data-write/persistence behavior.
• Performance: Constant unwrapping remains no-copy and is performed once at wrapper construction; no hot-path regression or redundant allocation was found.
• Additional user focus: none was provided. The complete PR was reviewed without further narrowing.

Review completion: converged in Round 2 with two inline findings and no unresolved candidate.

[github-actions]

[P1] Update the existing two-row mock-constant tests

This invariant is reached immediately by the existing non-disabled ScanNormalizePredicate.test_eval_const_conjuncts3 and test_eval_const_conjuncts4: lines 130 and 154 pass two-row non-const columns through MockFnCall::set_const_expr_col(), which constructs this wrapper outside any death/exception assertion. The normal BE-UT CMake glob includes exec/*.cpp, so those tests now abort or throw before reaching their remaining code. (The green macOS check only builds BE with MAKE_TEST=OFF.) Please update/remove those malformed fixtures, or assert the new failure at construction, together with this invariant.

[github-actions]

[P1] Assert the release-mode exception path here

This only behaves as a death assertion while DCHECKs are enabled. With NDEBUG, DORIS_CHECK_EQ uses the release comparison macro and doris_check_fail() throws doris::Exception; GoogleTest does not count leaving a death-test statement by exception as death. The existing be/test/common/check_test.cpp handles this contract by capturing the exception under NDEBUG and using EXPECT_DEATH only under DCHECK_IS_ON(). Please mirror that split (or use a build-mode-neutral helper), otherwise release BE-UT fails this new test.

[Mryange]

run buildall