pkg/environment: Migrate fs functions to fsx

pkg/environment/environment.go

@@ -1,25 +1,3 @@
 package environment
 
-import (
-	"io"
-	"io/fs"
-)
-
-// Environment represents an environment that a program can run it.
-// It mostly mimics the interfaces of the [os] package.
-type Environment interface {
-	isEnv()
-
-	Create(path string, mode fs.FileMode) (WritableFile, error)
-	Mkdir(path string, mode fs.FileMode) error
-	MkdirAll(path string, mode fs.FileMode) error
-}
-
-type WritableFile interface {
-	fs.File
-	io.Writer
-}
-
-func init() {
-	var _ Environment = new(Native)
-}
+type Environment struct{}