OpenApi plugin fails if output directory does not exist

[mjperlini]

Description and expected behavior
When running the openapi generator, the process fails as follows:

An unexpected error occurred:
Error: ENOENT: no such file or directory

Environment (please complete the following information):

• ZenStack version: 2.3.1
• Prisma version: 6.5
• Database type: Sqlite

Additional context
The other plugins call 'ensureEmptyDir' which creates the directory if it doesn't exist. The openapi plugin (both rest-generator and rpc-generator) doesn't call this function, so the plugin fails if the directory doesn't exist.

[ymc9]

Fixed in 2.14.0