[FEAT]: add 'owner' property to 'github_actions_runner_group' resource

[cringdahl]

Describe the need

As an enterprise user, I have access to several orgs, each of which requires its own runner group. They each require fine grained repository access, so Terraform-created enterprise runner groups won't work. I'd therefore like to add the owner field to the github_actions_runner_group resource to be able to use one PAT to manage multiple runner groups for multiple orgs.

SDK Version

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API Version

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Relevant log output

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