[fix][cp] UT only for 'fix: Unloaded lazy vector in duplicate field project

[guhaiyan0221]

What problem does this PR solve?

Issue Number: discussion #191

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 🚀 Performance improvement (optimization)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)
• 🔨 Refactoring (no logic changes)
• 🔧 Build/CI or Infrastructure changes
• 📝 Documentation only

Description

Bolt has already fixed the overflow error; still cherry-pick the UT to ensure the mentioned case is covered

Summary:
The following error was noticed when running a query as below, where the filter expressions were for one field and duplicate projects were for another field.

SELECT id, id FROM tmp WHERE name = 'John'

The lazy vector is not preloaded because it’s only referenced in identity projections, not in expressions, and the fillOutput calls wrapInDictionary multiple times on the same lazy vector. The lazy vector is still unloaded at the time, and thus, the dictionary vector wraps the same underlying lazy vector multiple times while unloaded.

This PR fixes this issue by caching the already wrapped children to avoid wrapping the same child multiple times.

Performance Impact

• No Impact: This change does not affect the critical path (e.g., build system, doc, error handling).

• Positive Impact: I have run benchmarks.

  Click to view Benchmark Results

  Paste your google-benchmark or TPC-H results here.
  Before: 10.5s
  After:   8.2s  (+20%)
  

• Negative Impact: Explained below (e.g., trade-off for correctness).

Release Note

Please describe the changes in this PR

Release Note:

Release Note:
- Fixed a crash in `substr` when input is null.
- optimized `group by` performance by 20%.

Checklist (For Author)

• I have added/updated unit tests (ctest).
• I have verified the code with local build (Release/Debug).
• I have run clang-format / linters.
• (Optional) I have run Sanitizers (ASAN/TSAN) locally for complex C++ changes.
• No need to test or manual test.

Breaking Changes

• No

• Yes (Description: ...)

  Click to view Breaking Changes

  Breaking Changes:
  - Description of the breaking change.
  - Possible solutions or workarounds.
  - Any other relevant information.
  

[Weixin-Xu]

LGTM