[Workspace] Pass filesystem when creating workspace
[Workspace] Pass filesystem when creating workspace

Once this is all wired up we can run workspaces tests in-memory.

JGiola/swift-package-manager,JGiola/swift-package-manager,vmanot/swift-package-manager,sschiau/swift-package-manager,sschiau/swift-package-manager,apple/swift-package-manager,abertelrud/swift-package-manager,sschiau/swift-package-manager,apple/swift-package-manager,sschiau/swift-package-manager,vmanot/swift-package-manager,JGiola/swift-package-manager,abertelrud/swift-package-manager,abertelrud/swift-package-manager,abertelrud/swift-package-manager,apple/swift-package-manager,apple/swift-package-manager,abertelrud/swift-package-manager,vmanot/swift-package-manager,sschiau/swift-package-manager,apple/swift-package-manager,JGiola/swift-package-manager,vmanot/swift-package-manager,vmanot/swift-package-manager,JGiola/swift-package-manager