feat: lint unused variables in Zarf packages

[AustinAbro321]

Description

Zarf dev lint will tell you when you have variables defined in your zarf file or that are set that are not being used by any files

Related Issue

Relates to #2064 Relates to #2096

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] New feature (non-breaking change which adds functionality)
• [ ] Other (security config, docs update, etc)

Checklist before merging

• [ ] Test, docs, adr added or updated as needed
• [ ] Contributor Guide Steps followed

[netlify[bot]]

✅ Deploy Preview for zarf-docs canceled.

Name	Link
🔨 Latest commit	5e0d89a4a3960b4d24c590696d329b9ff48674b4
🔍 Latest deploy log	https://app.netlify.com/sites/zarf-docs/deploys/65a6e911492fdd0008ae16f4

[AustinAbro321]

This will wait on #2276 as the re-architecture of variables will make this PR easier

[AustinAbro321]

This feature is not a high enough priority and too much has changed in the code to reasonably merge this. Closing to be re-added at a future date