feat: add BufWriter and extend buffered I/O traits and impls

[Anekoique]

This pull request introduces a new BufWriter type for buffered writing, expands trait implementations for references, and adds new utility methods for buffered I/O. It also makes some dependency and import updates to support these features.

Buffered I/O Enhancements:

• Added a new BufWriter type for buffered writing, including its implementation and integration into the public API. This allows efficient batched writes similar to BufReader for reads. (src/buffered/writer.rs, src/buffered/mod.rs, src/lib.rs, src/prelude.rs)
• Introduced the BufWrite trait, analogous to BufRead, with methods for flushing internal buffers, skipping bytes, and writing plain-old-data (POD) types. (src/lib.rs)
• Added new methods to BufRead: read_val for reading POD types and read_cstring for reading C-style strings. (src/lib.rs)

Trait Implementation Improvements:

• Implemented Read, Write, Seek, BufRead, and BufWrite for mutable references to types that implement those traits, improving composability and ergonomics. (src/impls.rs)
• Updated imports to include necessary types for these new implementations. (src/impls.rs)

Dependency and Code Organization:

• Added the bytemuck crate (with the derive feature) as a dependency to enable safe POD reads and writes. (Cargo.toml)
• Moved the DEFAULT_BUF_SIZE constant to a shared location and updated its usage for consistency. (src/buffered/mod.rs, src/buffered/reader.rs, src/buffered/writer.rs)

These changes collectively modernize and extend the buffered I/O capabilities of the crate, making it easier to use and more feature-rich.

After that, I will submit a PR to support netlink based on this PR.

[AsakuraMizu]

Plz move this PR to https://github.com/arceos-org/axio/tree/dev. Also, I may need to completely refactor this crate before accepting your PR. I sincerely apologize for this.

[Anekoique]

I will mark Starry-OS/arceos#25 and Starry-OS/StarryOS#71 as ready for review after the refactoring of the crate is completed.