Shave bytecode off the Vault

[jubeira]

Description

Just targeting simple low-hanging fruits that shouldn't change the logic at all:

• Use unchecked math whenever it's obvious it won't overflow (i.e. right next to if / else clauses)
• Move external getters to extension
• Eliminate unnecessary operations by visual inspection

This is enough to make the Vault deployable again.

Type of change

• [ ] Bug fix
• [ ] New feature
• [ ] Breaking change
• [ ] Dependency changes
• [ ] Code refactor / cleanup
• [x] Optimization: [ ] gas / [x] bytecode
• [ ] Documentation or wording changes
• [ ] Other

Checklist:

• [x] The diff is legible and has no extraneous changes
• [x] Complex code has been commented, including external interfaces
• [x] Tests have 100% code coverage
• [x] The base branch is either main, or there's a description of how to merge

Issue Resolution

N/A