feat: default-required feature flag

[Noxsios]

Description

Refer to adr/0025-required-optional.md.

Related Issue

Fixes #2059

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

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

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[Noxsios]

TODO:

• [x] Talk w/ @Racer159 about composition behavior
• [x] Discuss zarf-seed-registry import behavior
• [x] Think about migration behavior
• [x] Lint addition?
• [x] zarf package migrate?

[Noxsios]

Some final thoughts for review:

• Unit testing filters?
• config.CommonOptions.Confirm behavior w/ filters.NewDeploymentFilter
• zarf dev migrate opinionated YAML transformations
• zarf dev migrate RunE vs Run
• ADR updates