async overload for `Command.run(using context: CommandContext, signature: Signature)`

[finestructure]

In the context of converting a code base using Vapor commands for batch jobs to Swift 5.5's async/await, the issue arose that run does not have an async overload. This poses the following problem when converting

fun run(using context: CommandContext, signature: Signature) throws {
  try f.wait()
}

where f is func f() → EventLoopFuture<Void>.

A workaround is to use

    func run(using context: CommandContext, signature: Signature) throws {
        let promise = context.application.eventLoopGroup.next()
            .makePromise(of: Void.self)
        promise.completeWithAsync {
            try await f()
        }
        try promise.futureResult.wait()
    }

but it would be nice if this wrapper (or simply handling via @main, if possible, or some other solution) existed upstream such that one could simply write

    func run(using context: CommandContext, signature: Signature) async throws {
      try await f()
    }