This will allow for registering rules that aren't compiled as part of
SwiftLintFramework.
Specifically this will allow us to split the built-in and extra rules
into separate modules, leading to faster incremental compilation when
working on rules since the rest of the framework won't need to be
rebuilt on every compilation.
To support this, we first must use an async entrypoint to the CLI, which
we do by changing the lint and analyze commands to conform to
`AsyncParsableCommand`.
The in order to map over the closures with suspension points, we pull in
CollectionConcurrencyKit as a new dependency.
This change does not touch SwiftLintFramework, only the CLI target.
Martin Redington
JP SimardandDanny Mösch