Update list_topsorted_dependencies script. (#723)
Update list_topsorted_dependencies script. (#723)

Motivation:

Newer versions of SwiftPM for the Swift 5 release have changed the output
format of swift package dump-package. This has broken our
list_topsorted_dependencies script. This script is highly useful, so we'd
like to keep it working.

The discussion on SR-9191 suggests that SwiftPM considers this format
changeable at any time, so we may need to make a change like this in future.
We may want to consider writing tests for this script to ensure its continued good functioning.

Modifications:

- Amended the jq scripts to parse the new JSON format.

Result:

list_topsorted_dependencies will work with Swift 5 development copies of
SwiftPM. Note that this will break this script with earlier copies of SwiftPM,
but as we only support Swift 5 on the master branch this change is safe to
make.
apple/swift-nio,apple/swift-nio,apple/swift-nio,apple/swift-nio,apple/swift-nio