Support Xcode 13 automatic versioning


Description of the feature request

It would be no more need to bump app versions using a Step.

Use case / for what or how I would use it


From Xcode 13 release notes:
When uploading an app to App Store Connect, the distribution assistant in Xcode detects whether your app has a valid build number (CFBundleVersion). If your app has an invalid number (like one that was used previously, or precedes your current build number), the distribution assistant provides an option to automatically increment it to a valid number. In addition, the distribution assistant ensures that the build numbers of all embedded content in your app (such as app extensions, App Clips, or watchOS apps) are in sync with your app. Note that this doesn’t modify your source code or your archive; Xcode updates the build number in a staged copy of your app before packaging and uploading it to App Store Connect. (59826409)

There is a new related key available in ExportOptions.plist:

Should Xcode manage the app's build number when uploading to App Store Connect? Defaults to YES.```