Implement automatic port reassignment on Windows

While only leveraged by the WSL backend, this commit also adds core
infrastructure for all other backends for future enhancement.

- Adds a common port cross backend allocation registry to prevent duplicate
  assignment across multiple machine instances
- Introduces logic in Start() that detects OS port conflicts and scans for a
  viable replacement port
- Updates connection definitions and server configuration accordingly
- Utilizes a coordinated file lock strategy to prevent racing overwrites of port
  and connection registries
- WSL backend coordinates locking for containers.conf until a future common
  enhancement exists to replace it

[NO NEW TESTS NEEDED]

Signed-off-by: Jason T. Greene <jason.greene@redhat.com>

pkg/machine/config.go

@@ -199,6 +199,17 @@ func GetDataDir(vmType VMType) (string, error) {
 	return dataDir, mkdirErr
 }
 
+// GetGLobalDataDir returns the root of all backends
+// for shared machine data.
+func GetGlobalDataDir() (string, error) {
+	dataDir, err := DataDirPrefix()
+	if err != nil {
+		return "", err
+	}
+
+	return dataDir, os.MkdirAll(dataDir, 0755)
+}
+
 // DataDirPrefix returns the path prefix for all machine data files
 func DataDirPrefix() (string, error) {
 	data, err := homedir.GetDataHome()