fix: resolve exported type stuttering issues (revive)

- Rename VaultMetadata to Metadata in internal/vault package to avoid stuttering
- Rename BIP85DRNG to DRNG in pkg/bip85 package to avoid stuttering
- Update all references in code and tests

internal/secret/secret.go

@@ -78,6 +78,7 @@ func (s *Secret) Save(value []byte, force bool) error {
 	}
 
 	Debug("Successfully saved secret", "secret_name", s.Name)
+
 	return nil
 }
 
@@ -220,6 +221,7 @@ func (s *Secret) LoadMetadata() error {
 		CreatedAt: now,
 		UpdatedAt: now,
 	}
+
 	return nil
 }
 
@@ -278,6 +280,7 @@ func GetCurrentVault(fs afero.Fs, stateDir string) (VaultInterface, error) {
 	if getCurrentVaultFunc == nil {
 		return nil, fmt.Errorf("GetCurrentVault function not registered")
 	}
+
 	return getCurrentVaultFunc(fs, stateDir)
 }