Refactor packager struct properties

[phillebaba]

Describe what should be investigated or refactored

While working on #2682 I realized that packager makes use of a lot of struct properties in place of local variables or function arguments. This made the work very difficult. So before we can clean up packager the use of all struct properties that are not thread safe has to be removed.

Links to any relevant code

(optional) i.e. - https://github.com/defenseunicorns/zarf/blob/main/README.md?plain=1#L1

Additional context

N/A