Refactor physical pointer API

[sangho2]

This PR refactors the physical pointer API.

[wdcui]

@CvvT I think we should take a look at this PR as well. Thanks!

[wdcui]

I left some comments below. I'm confident about my review because this PR has a lot of subtlties, so I didn't approve it and asked Weiteng to take a look at it as well.

[lschuermann]

I want to take a slightly more in-depth pass over lib.rs, but otherwise this looks pretty good to me!

It's hard to judge what this + the other changes in #817 look like. Is it work merging this one into the sanghle/lvbs/vmap_copy branch first, and then doing another thorough pass over the merged result to make sure it's consistent?

Given the comparisons between this infrastructure and DMA, maybe it's worth looking at tock/tock#4702? That PR to Tock addresses two separate but related concerns:

• It prevents the Rust compiler from making incorrect assumptions about the state of memory it can dereference (Rust slices). This is not directly applicable here, as memory is only ever accessed through asm!()-backed memcpy helpers, so there is no buffer with "shared custody" between Rust and the foreign entity.
• It emits the appropriate synchronization instructions (i.e., fences) for when Rust-issued writes need to be made visible to the foreign entity, or when foreign-issued writes need to be made visible to Rust. This may still be missing here.

[github-actions]

ℹ️ Note: This semver check was run against the sanghle/lvbs/vmap_copy branch, not main or ulitebox.

🤖 SemverChecks 🤖 ⚠️ Potential breaking API changes detected ⚠️

Click for details

--- failure derive_trait_impl_removed: built-in derived trait no longer implemented ---

Description:
A public type has stopped deriving one or more traits. This can break downstream code that depends on those types implementing those traits.
        ref: https://doc.rust-lang.org/reference/attributes/derive.html#derive
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.48.0/src/lints/derive_trait_impl_removed.ron

Failed in:
  type PhysConstPtr no longer derives Clone, in /home/runner/work/litebox/litebox/litebox_common_linux/src/physical_pointers.rs:417
  type PhysMutPtr no longer derives Clone, in /home/runner/work/litebox/litebox/litebox_common_linux/src/physical_pointers.rs:88

--- failure struct_missing: pub struct removed or renamed ---

Description:
A publicly-visible struct cannot be imported by its prior path. A `pub use` may have been removed, or the struct itself may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.48.0/src/lints/struct_missing.ron

Failed in:
  struct litebox_common_linux::vmap::PhysPageMapInfo, previously in file /home/runner/work/litebox/litebox/target/semver-checks/git-sanghle_lvbs_vmap_copy/acd6ae561116135b6915cf113a535d2c2e02cfc9/litebox_common_linux/src/vmap.rs:111

--- failure trait_associated_type_added: non-sealed public trait added associated type without default value ---

Description:
A non-sealed trait has gained an associated type without a default value, which breaks downstream implementations of the trait
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#trait-new-item-no-default
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.48.0/src/lints/trait_associated_type_added.ron

Failed in:
  trait associated type litebox_common_linux::vmap::VmapManager::MapInfo in file /home/runner/work/litebox/litebox/litebox_common_linux/src/vmap.rs:22

--- failure trait_unsafe_added: pub trait became unsafe ---

Description:
A publicly-visible trait became `unsafe`, so implementing it now requires an `unsafe impl` block.
        ref: https://doc.rust-lang.org/book/ch19-01-unsafe-rust.html#implementing-an-unsafe-trait
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.48.0/src/lints/trait_unsafe_added.ron

Failed in:
  trait litebox_common_linux::vmap::VmapManager in file /home/runner/work/litebox/litebox/litebox_common_linux/src/vmap.rs:19