etcd-snapshot --s3 should use the rke2-server config files s3 settings

[mitchellmaler]

Is your feature request related to a problem? Please describe.
Would like to kick off an on demand s3 snapshot but the cli requires all the same s3 arguments that are already in the server config yaml file.

Describe the solution you'd like
Allow the rke2 etcd-snapshot --s3 command to read from the default server config file and use the same settings that are used by the scheduled snapshot.

Describe alternatives you've considered
None

[brandond]

Duplicate of #1628