Implement ByteValued for i128/u128

[roypat]

Summary of the PR

Implements ByteValued for u128/i128, as well as arrays of them.

I also looked at turning the array implementations into one using const generics (to remove the restriction on them being only implemented for array sizes up to 32), but a combination of Default being a super trait of ByteValued and https://github.com/rust-lang/rust/issues/61415 make this impossible

Requirements

Before submitting your PR, please make sure you addressed the following requirements:

• [x] All commits in this PR are signed (with git commit -s), and the commit message has max 60 characters for the summary and max 75 characters for each description line.
• [x] All added/changed functionality has a corresponding unit/integration test.
• [x] All added/changed public-facing functionality has entries in the "Upcoming Release" section of CHANGELOG.md (if no such section exists, please create one).
• [x] Any newly added unsafe code is properly documented.

[vireshk]

superseded by https://github.com/rust-vmm/vm-memory/pull/242