feat(bytesbuf): impl ThreadAware for GlobalPool

[sandersaares]

Summary

Make GlobalPool internally thread-aware by replacing std::sync::Arc<GlobalPoolInner> with thread_aware::Arc<GlobalPoolInner, PerCore>. This gives each core its own independent pool on relocation, providing better UX and integration into thread-isolated runtime environments.

Changes

• Added thread_aware dependency to bytesbuf crate (with derive feature)
• Changed GlobalPool.inner from Arc<GlobalPoolInner> to thread_aware::Arc<GlobalPoolInner, PerCore>
• Derived ThreadAware for GlobalPool
• Updated allowed_external_types to include thread_aware types exposed in public API
• Added ThreadAware static assertion and relocation smoke test

Notes

• No API breaking changes — GlobalPool::new(), reserve(), Clone, Debug, Memory, and MemoryShared all continue to work identically
• The only addition is the new ThreadAware impl
• Block release across threads continues to work safely because each GlobalPoolInner sub-pool uses Arc<Mutex<...>>

Closes #270

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.0%. Comparing base (5cae290) to head (ad8466e).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #273   +/-   ##
=======================================
  Coverage   100.0%   100.0%           
=======================================
  Files         141      141           
  Lines        8626     8631    +5     
=======================================
+ Hits         8626     8631    +5     

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[github-actions]

⚠️ Breaking Changes Detected

--- failure auto_trait_impl_removed: auto trait no longer implemented ---

Description:
A public type has stopped implementing one or more auto traits. This can break downstream code that depends on the traits being implemented.
        ref: https://doc.rust-lang.org/reference/special-types-and-traits.html#auto-traits
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.46.0/src/lints/auto_trait_impl_removed.ron

Failed in:
  type GlobalPool is no longer UnwindSafe, in /home/runner/work/oxidizer/oxidizer/crates/bytesbuf/src/mem/global.rs:39
  type GlobalPool is no longer RefUnwindSafe, in /home/runner/work/oxidizer/oxidizer/crates/bytesbuf/src/mem/global.rs:39

If the breaking changes are intentional then everything is fine - this message is merely informative.

Remember to apply a version number bump with the correct severity when publishing a version with breaking changes (1.x.x -> 2.x.x or 0.1.x -> 0.2.x).