Refactored allocator-api2 reexports

[bavshin-f5]

See individual commits.

unsize_box is a temporary solution, I'll revert and properly reexport it once I have time to send a patch to the upstream project.

[Copilot]

Pull Request Overview

This PR centralizes and cleans up allocator-api2 reexports by introducing a dedicated collections module, adjusting allocator exports, and updating associated imports and examples.

• Added a top-level collections module to reexport collection types from allocator-api2.
• Updated internal core imports and example code to use the new collections paths.
• Refactored allocator reexports (moved Global, narrowed boxed export to Box) and added a custom unsize_box macro.
• Enhanced Cargo.toml with a new serde feature flag for serialization support.

Reviewed Changes

Copilot reviewed 7 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/lib.rs	Added pub mod collections to expose the new collections module.
src/core/string.rs	Switched imports to crate::collections::{TryReserveError, Vec}.
src/core/mod.rs	Removed pub mod rbtree and its pub use in favor of reexports from the collections module.
src/collections/mod.rs	Introduced collections module reexporting TryReserveError, Vec, and RbTreeMap.
src/allocator.rs	Adjusted Global and Box exports, removed broad collections/vec exports, and added unsize_box.
examples/shared_dict.rs	Updated example imports to use ngx::collections::RbTreeMap.
Cargo.toml	Added serde feature for allocator-api2/serde.

Comments suppressed due to low confidence (4)

src/core/mod.rs:3

• Removing the rbtree export from core is a breaking API change. Consider documenting this in the CHANGELOG or providing a deprecation path for downstream users.

pub mod slab;

src/allocator.rs:98

• The new unsize_box macro is public API—consider adding unit tests or examples to validate its behavior and edge cases.

#[macro_export]

Cargo.toml:45

• [nitpick] Indentation for the serde feature block differs from the surrounding feature definitions. Align formatting with alloc and std blocks for consistency.

serde = [

[xeioex]

Looks good.