Type-level register reference read/write permissions

[Dentosal]

Requires #804.

Introduce RegR and RegW types for type-level-permissioned register access.

Needs new tests, some old ones need fixing.

Checklist

• Breaking changes are clearly marked as such in the PR description and changelog
• New behavior is reflected in tests
• If performance characteristic of an instruction change, update gas costs as well or make a follow-up PR for that
• The specification matches the implemented behavior (link update PR if changes are needed)

Before requesting review

• I have reviewed the code myself
• I have created follow-up issues caused by this PR and linked them here

After merging, notify other teams

• Rust SDK
• Sway compiler