feat: compile-time feature-gated Rust backtrace for JNI error diagnostics

[summaryzb]

No regression for release builds, Python layer also can reuse this mechanism

The overall design employs a two-tiered strategy of "compile-time switching + runtime gating":

1. Compile-time switching: Two versions of the MaybeBacktrace type are defined through conditional compilation using #[cfg(feature = "backtrace")], when the feature is disabled error size, layout, and runtime behavior are unchanged as before

2. Runtime Gating: With the backtrace feature enabled, actual backtrace capture is still controlled by the runtime environment variable RUST_BACKTRACE=1

3. Java integration: The transformation logic calls err.backtrace() to obtain an optional backtrace. If exists, it is passed to the corresponding Java exception class. Users can enable this feature during Maven builds using -Drust.features=backtrace.

[github-actions]

ACTION NEEDED
Lance follows the Conventional Commits specification for release automation.

The PR title and description are used as the merge commit message. Please update your PR title and description to match the specification.

For details on the error please inspect the "PR Title Check" action.

[summaryzb]

@hamersaw PTAL

[codecov]

Codecov Report

❌ Patch coverage is 62.50000% with 24 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
rust/lance-core/src/error.rs	62.50%	24 Missing ⚠️

📢 Thoughts on this report? Let us know!