feat(block): optimize ramdisk, add static variant

[eternalcomet]

• Redesigned the heap-backed RAM disk to use a raw heap allocation (NonNull<[u8]>) instead of a Vec<u8>, beacause we doesn't use any method in Vec.
• Added a static variant that utilizes an existing memory region as a RAM disk, enabling the use of the initrd image loaded into memory by the bootloader.

[Copilot]

Pull request overview

This PR optimizes the RAM disk implementation and adds a new static RAM disk variant. The heap-backed RAM disk is refactored from using Vec<u8> to a raw heap allocation with NonNull<[u8]>, and a new static RAM disk driver that operates on statically allocated memory buffers is introduced.

Key Changes

• Refactored heap-backed RAM disk to use NonNull<[u8]> instead of Vec<u8> for more direct memory management
• Added new ramdisk_static.rs module providing a RAM disk backed by a 'static mut [u8] buffer
• Added ramdisk-static feature flag to Cargo.toml

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 10 comments.

File	Description
axdriver_block/src/ramdisk.rs	Refactored to use raw heap allocation with manual memory management instead of Vec
axdriver_block/src/ramdisk_static.rs	New static RAM disk implementation for statically allocated buffers
axdriver_block/src/lib.rs	Added ramdisk_static module export with feature gate
axdriver_block/Cargo.toml	Added ramdisk-static feature flag and reorganized features alphabetically

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[AsakuraMizu]

Update on 1.13: considering using Tagged pointer to save a usize.