Prevent array_position panic for minimum start positions

[1fanwang]

Which issue does this PR close?

• Closes panic: array_position underflows start_from at i64::MIN #22220.

Rationale for this change

array_position accepts an optional one-based start position. Passing -9223372036854775808 currently aborts evaluation with:

datafusion/functions-nested/src/position.rs:210:21:
attempt to subtract with overflow

It now returns the normal execution error start_from out of bounds: -9223372036854775808.

What changes are included in this PR?

The one-based-to-zero-based conversion now uses checked subtraction in both optimized and generic execution paths.

What is the testing strategy for this PR?

SQL regressions exercise a scalar start position, a column start position with a scalar needle, and column start and needle values.

Raw results

$ git checkout upstream/main -- datafusion/functions-nested/src/position.rs
$ cargo test -p datafusion-sqllogictest --test sqllogictests -- array_position
thread 'tokio-rt-worker' panicked at datafusion/functions-nested/src/position.rs:210:21:
attempt to subtract with overflow
Error: Execution("1 failures")

$ git checkout HEAD -- datafusion/functions-nested/src/position.rs
$ cargo test -p datafusion-sqllogictest --test sqllogictests -- array_position
Running with 12 test threads (available parallelism: 12)
Progress: 1/1 files completed (100%)

$ RUST_BACKTRACE=1 cargo test --profile ci \
    --exclude datafusion-examples --exclude datafusion-benchmarks --exclude datafusion-cli \
    --workspace --lib --tests --bins \
    --features avro,json,backtrace,extended_tests,recursive_protection,parquet_encryption
passed=10997 ignored=8

Are there any user-facing changes?

Yes. An invalid minimum Int64 start position returns an execution error instead of panicking.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.61%. Comparing base (17547e2) to head (6fff9d8).
⚠️ Report is 25 commits behind head on main.

Files with missing lines	Patch %	Lines
datafusion/functions-nested/src/position.rs	92.85%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24838      +/-   ##
==========================================
+ Coverage   81.58%   81.61%   +0.03%     
==========================================
  Files        1123     1123              
  Lines      406743   409401    +2658     
  Branches   406743   409401    +2658     
==========================================
+ Hits       331840   334152    +2312     
- Misses      55464    55629     +165     
- Partials    19439    19620     +181     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[jayzhan211]

Thanks @1fanwang , LGTM