feat: static System priority

[Autsider666]

===:clipboard: PR Checklist :clipboard:===

• [x] :pushpin: issue exists in github for these changes
• [x] :microscope: existing tests still pass
• [x] :see_no_evil: code conforms to the style guide
• [x] :triangular_ruler: new tests written and passing / old tests updated with new scenario(s)
• [x] :page_facing_up: changelog entry added (or not needed)

==================

Closes #3102

Changes:

• Refactored System.priority to be static
• Updated priority in all systems
• Updated priority sort in SystemManager

[eonarheim]

@Autsider666 Thanks for the PR, this looks perfect. Just a few failing tests that need a small refactor to account for the static.

Apologies about the late review I'm catching up on a few things.

[eonarheim]

Ope I accidentally added commits on main before merging doh! Should be fine

[eonarheim]

@Autsider666 Thanks again!