[refactor]: Internalize loader api

This PR intends to move the loader api to
internal. Only the necessary methods which
are needed for the api have been put into
`pkg/loader.go`.

Signed-off-by: Varsha Prasad Narsing <varshaprasad96@gmail.com>

api/pkg/loader/loader.go

@@ -0,0 +1,24 @@
+// Copyright 2023 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+// Package pkg has all the helpers to interact with the api.
+package loader
+
+import (
+	"sigs.k8s.io/kustomize/api/internal/loader"
+	"sigs.k8s.io/kustomize/kyaml/filesys"
+)
+
+// NewFileLoaderAtCwd returns a loader that loads from PWD.
+// A convenience for kustomize edit commands.
+func NewFileLoaderAtCwd(fSys filesys.FileSystem) *loader.FileLoader {
+	return loader.NewLoaderOrDie(
+		loader.RestrictionRootOnly, fSys, filesys.SelfDir)
+}
+
+// NewFileLoaderAtRoot returns a loader that loads from "/".
+// A convenience for tests.
+func NewFileLoaderAtRoot(fSys filesys.FileSystem) *loader.FileLoader {
+	return loader.NewLoaderOrDie(
+		loader.RestrictionRootOnly, fSys, filesys.Separator)
+}