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

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