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/konfig/builtinpluginconsts/namesuffix.go

@@ -0,0 +1,11 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package builtinpluginconsts
+
+const (
+	nameSuffixFieldSpecs = `
+nameSuffix:
+- path: metadata/name
+`
+)