feat: Add config option to prefer GET request over LIST when using Hashicorp Vault (#8049)

## Summary
Hashicorp Vault prefers a `LIST` HTTP method to be used when fetching
secrets but not all environments will allow custom http methods through
WAFs. This PR adds `N8N_EXTERNAL_SECRETS_PREFER_GET` which when set to
`true` will use GET instead of LIST to fetch secrets.


## Review / Merge checklist
- [x] PR title and summary are descriptive. **Remember, the title
automatically goes into the changelog. Use `(no-changelog)` otherwise.**
([conventions](https://github.com/n8n-io/n8n/blob/master/.github/pull_request_title_conventions.md))

packages/cli/src/config/schema.ts

@@ -1032,6 +1032,12 @@ export const schema = {
 			env: 'N8N_EXTERNAL_SECRETS_UPDATE_INTERVAL',
 			doc: 'How often (in seconds) to check for secret updates.',
 		},
+		preferGet: {
+			format: Boolean,
+			default: false,
+			env: 'N8N_EXTERNAL_SECRETS_PREFER_GET',
+			doc: 'Whether to prefer GET over LIST when fetching secrets from Hashicorp Vault.',
+		},
 	},
 
 	deployment: {