feat: Add github_organization_network_configuration resource

[austenstone]

Overview

This PR adds a new github_organization_network_configuration resource to manage GitHub organization network configurations for hosted compute services.

It also adds the missing linkage for GitHub-hosted private networking on github_actions_runner_group via network_configuration_id, so hosted runners can consume private networking through their assigned runner group.

What this PR adds

• New resource: github_organization_network_configuration
• Full CRUD support for organization network configurations
• Import support for organization network configurations
• Support for github_actions_runner_group.network_configuration_id
• Acceptance coverage for:
  • create, update, and import flows for github_organization_network_configuration
  • create, update, import, and clear flows for runner group network configuration association
• Documentation updates for:
  • github_organization_network_configuration
  • github_actions_runner_group
  • github_actions_hosted_runner
• Example updates for hosted runners and public IP configuration

Schema

github_organization_network_configuration

• name (Required) - Network configuration name (1-100 chars, alphanumeric plus ._-)
• compute_service (Optional) - Hosted compute service: none or actions (default: none)
• network_settings_ids (Required) - Exactly one network settings ID
• created_on (Computed) - Creation timestamp
• id (Computed) - Resource ID

github_actions_runner_group

• network_configuration_id (Optional) - The ID of the hosted compute network configuration associated with the runner group for GitHub-hosted private networking

Notes

• This resource is organization-scoped and validates organization mode via checkOrganization().
• GitHub private networking for GitHub-hosted runners is configured on the runner group, not directly on github_actions_hosted_runner.
• For Azure private networking, network_settings_ids must use the GitHub-facing network settings identifier (GitHubId), not the Azure ARM resource ID.
• Network configurations are available for GitHub Enterprise Cloud organizations.

Validation

• go test ./github -run TestAccGithubOrganizationNetworkConfiguration -count=1
• go test ./github -run TestAccGithubActionsRunnerGroup -count=1
• go test ./github -run '^$' -count=1

[deiga]

@austenstone We've now upgraded go-github to latest. Could you rebase onto main now? :)

[austenstone]

Healthy from my side ✅

I re-tested the full flow and everything is behaving as expected: create/update/destroy all work cleanly, CI is green, and the acceptance coverage passes. I also validated the real-world integration path with org network configurations, runner group association, and hosted runner private networking.

[deiga]

Partial review

[austenstone]

I opened a separate pull request for the Enterprise level. We can either stack these PRS or just merge the Enterprise one.

[austenstone]

closing in favor of #3274