Add data source for resources and groups

[jan-opal]

Description of the change

Adds data sources for resources and groups. Currently the only way to retrieve them is via the Opal ID. A possible later addition could be to allow doing this via things like:

1. name + resource type (fail if no unique result)
2. remote info (i.e. AWS ARN, Okta group ID, etc)

But for now this matches the pattern of the app data source and in a previous PR we also added the Opal IDs in the UI with easy click to copy button to make using these easier.

Testing

• tested fetching both group and resources via the IDs and using their attributes in other places

Checklist

• I performed a self-review of my code
• I manually tested my code change (please list details in description)
• I added unit tests
• I updated the changelog
• I updated the public facing docs

[linear]

OPAL-8088 Add groups / resources as data sources