refactor: move validate to expose it as receivers (#2419)

## Description

Moves `validate` behavior out of `internal` and onto receivers to their
given types. Since validation requires no external logic, this fits
better and has a cleaner experience. Additionally, validation can be
called against each type itself individually instead of only living at
the package level.

## 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](https://github.com/defenseunicorns/zarf/blob/main/CONTRIBUTING.md#developer-workflow)
followed

---------

Signed-off-by: razzle <[email protected]>
Co-authored-by: Austin Abro <[email protected]>

src/pkg/packager/composer/list.go

@@ -11,7 +11,6 @@ import (
  "strings"
 
  "github.com/defenseunicorns/pkg/helpers"
- "github.com/defenseunicorns/zarf/src/internal/packager/validate"
  "github.com/defenseunicorns/zarf/src/pkg/layout"
  "github.com/defenseunicorns/zarf/src/pkg/packager/deprecated"
  "github.com/defenseunicorns/zarf/src/pkg/utils"
@@ -142,7 +141,7 @@ func NewImportChain(head types.ZarfComponent, index int, originalPackageName, ar
  }
 
  // TODO: stuff like this should also happen in linting
- if err := validate.ImportDefinition(&node.ZarfComponent); err != nil {
+ if err := node.ZarfComponent.ValidateImportDefinition(); err != nil {
  return ic, err
  }