chore(all): return concrete types, accept interfaces

- Remove exported interfaces unused locally
- Define interfaces to accept arguments
- Return concrete types, not interfaces

internal/alpine/version.go

@@ -7,10 +7,6 @@ import (
 	"strings"
 )
 
-type VersionGetter interface {
-	Version(ctx context.Context) (version string, err error)
-}
-
 func (a *Alpine) Version(ctx context.Context) (version string, err error) {
 	file, err := os.OpenFile(a.alpineReleasePath, os.O_RDONLY, 0)
 	if err != nil {