CLI docs: include corresponding API operation ID for each command so we can link to it

[david-crespo]

While some users can probably figure out that our CLI commands usually correspond to a similarly-named API endpoint, we should link to the API endpoint from the CLI command. This is an especially big problem for commands with the dreaded --json-body arg, which requires detailed knowledge of the API request body.

https://docs.oxide.computer/cli/instance/create