feat: ExecutionMode control for Flexible Processing

[Eideren]

PR Details

See title

Related Issue

Fix #2532

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My change requires a change to the documentation.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have built and run the editor to try this change out.

[Doprez]

One question but functionally this looks good to me.

[Doprez]

Do we want the default to act like a regular EntityProcessor for the sake of consistency?

[Eideren]

I think most users would actually expect their processors to only run at runtime out of the box, like script do. I understand that it's a bit counter intuitive when you come from how EntityProcessor work out of the box, which is why I wanted to change that as well but that's a far bigger breaking change

[Doprez]

With the amount of times I have crashed the editor due to me forgetting to add ExecutionMode I fully agree with that logic.

Sounds good to me then.