Refactor the PrefixSuffixTransformer into separate prefix- and suffix transformers (#4318)

* Refactor prefix filter into its own filter, decoupled from the prefixsuffix filter

* Refactor prefix transformer into its own transformer, decoupled from the prefixsuffix transformer

* Refactor suffix filter into its own filter, decoupled from the prefixsuffix filter

* Refactor suffix transformer into its own transformer, decoupled from the prefixsuffix transformer

* Add a default nameSuffix field spec in addition to the namePrefix

* Remove the PrefixSuffixTransformer from the list of builtin transformers

* Add a multi-transformer to builtinhelpers.TransformFactories

* Remove the implementation of the prefixsuffixtransformer.PrefixSuffixTransformer

* Resolve style and format related feedback from the pull request

* Add test to test the legacy PrefixSuffixTransformer for BC purposes

api/krusty/legacyprefixsuffixtransformer_test.go

@@ -0,0 +1,41 @@
+// Copyright 2021 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package krusty_test
+
+import (
+	"testing"
+
+	kusttest_test "sigs.k8s.io/kustomize/api/testutils/kusttest"
+)
+
+func TestLegacyPrefixSuffixTransformer(t *testing.T) {
+	th := kusttest_test.MakeHarness(t)
+	th.WriteK(".", `
+resources:
+- service.yaml
+transformers:
+- |-
+  apiVersion: builtin
+  kind: PrefixSuffixTransformer
+  metadata:
+    name: notImportantHere
+  prefix: baked-
+  suffix: -pie
+  fieldSpecs:
+  - path: metadata/name
+`)
+	th.WriteF("service.yaml", `
+apiVersion: v1
+kind: Service
+metadata:
+  name: apple
+`)
+	m := th.Run(".", th.MakeDefaultOptions())
+	th.AssertActualEqualsExpected(m, `
+apiVersion: v1
+kind: Service
+metadata:
+  name: baked-apple-pie
+`)
+}