feat(runtime): enable current_thread_id on nightly

[Berrysoft]

They are equvalent on major targets.

[Copilot]

Pull request overview

This PR enables the use of Rust's nightly std::thread::current_id() API as a performance optimization for thread ID retrieval in the runtime. When the current_thread_id feature is enabled on nightly Rust, the code uses the standard library's optimized implementation instead of a thread-local storage fallback.

• Adds current_thread_id feature flag to enable nightly std::thread::current_id() API
• Refactors SendWrapper to conditionally use either the nightly API or thread-local fallback
• Includes the new feature in the nightly meta-feature for convenience

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
compio/Cargo.toml	Adds current_thread_id feature flag and includes it in the nightly meta-feature
compio-runtime/Cargo.toml	Defines the current_thread_id feature flag and includes it in nightly
compio-runtime/src/lib.rs	Adds feature gate to enable the nightly current_thread_id Rust feature
compio-runtime/src/runtime/send_wrapper.rs	Refactors thread ID retrieval to use std::thread::current_id() when feature is enabled, with fallback to thread-local implementation

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[George-Miao]

LGTM