CI: Add fixes for tagged release runs and assorted minor issues

* Add provisioning profile support for macOS builds
* Fix internal variable names in macOS packaging script
* Add fallback git reference for validator actions
* Add required repository environment to documention deployment jobs
* Pass GitHub pull request number to GitHub CLI explicitly
* Use shortened commit hash for Steam nightly versions
* Ensure that concurrency check for tagged push uses a boolean value
* Update disk image creation function to retry ejection on CI
* Fix repository checkout in Flatpak publish action
* Fix output paths and filenames of generated appcast XML files
* Limit notice about notarization password use to non-CI usage
* Remove architecture-specific suffix from appcast artifact name