feat: Add hosted runners URL and network configuration ID to runner group models

[austenstone]

Adds missing fields to runner group models based on the GitHub API documentation:

Added to RunnerGroup:

• HostedRunnersURL - URL for hosted runners in the group
• NetworkConfigurationID - Identifier for hosted compute network configuration

Added to CreateRunnerGroupRequest:

• NetworkConfigurationID - Network configuration when creating runner groups

Added to UpdateRunnerGroupRequest:

• NetworkConfigurationID - Network configuration when updating runner groups (can be null to unset)

All tests updated and passing.

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[gmlewis]

Thank you, @austenstone!
Please run step 4 of CONTRIBUTING.md and push the changes to this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.33%. Comparing base (025030e) to head (70d5a6a).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #3825 +/- ##
=======================================
Coverage 92.33% 92.33% =======================================
Files 194 194 Lines 13990 13990 =======================================
Hits 12917 12917 Misses 884 884 Partials 189 189 

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[gmlewis]

Thank you, @austenstone!
LGTM.
Merging.