Replace calls to Invoke-GitHubAPI.ps1 with calls to GH CLI

[danieljurek]

The gh CLI offers many of the features we use today (release creation, issue creation, PR creation, etc.) in a more convenient interface: https://cli.github.com/manual/

For authenticated calls that aren't directly supported by features there is [gh api](https://cli.github.com/manual/gh_api)

Authentication is transparent and can use GH_TOKEN environment variable.

The gh CLI is already present on Azure DevOps agents. Incomplete list of examples:

• Windows 2022 -- https://github.com/actions/virtual-environments/blob/main/images/win/Windows2022-Readme.md#cli-tools
• Windows 2019 -- https://github.com/actions/virtual-environments/blob/main/images/win/Windows2019-Readme.md#cli-tools
• Ubuntu 20 -- https://github.com/actions/virtual-environments/blob/main/images/linux/Ubuntu2004-Readme.md#cli-tools
• MacOS 11 -- https://github.com/actions/virtual-environments/blob/main/images/macos/macos-11-Readme.md#utilities

[kurtzeborn]

There is a larger topic to discuss on whether we want GH CLI as a dependency on our pipelines. It handles errors differently than PowerShell too, so we'd want to be sure we get sufficient benefit for the added complexity of doing this.

CC: @weshaggard