Fix revive package stuttering errors

- Rename SecretMetadata to Metadata in secret package
- Rename SecretVersion to Version in secret package
- Update NewSecretVersion to NewVersion function
- Update all references across the codebase including:
  - vault package aliases
  - CLI usage
  - test files
  - method receivers and signatures

internal/secret/metadata.go

@@ -20,8 +20,8 @@ type UnlockerMetadata struct {
 	Flags     []string  `json:"flags,omitempty"`
 }
 
-// SecretMetadata contains information about a secret
-type SecretMetadata struct {
+// Metadata contains information about a secret
+type Metadata struct {
 	CreatedAt time.Time `json:"createdAt"`
 	UpdatedAt time.Time `json:"updatedAt"`
 }