Add a test case for issue 4905

```
===== ACTUAL BEGIN ========================================
apiVersion: v1
data:
  config.yaml: "null"
kind: ConfigMap
metadata:
  name: issue4905
===== ACTUAL END ==========================================
   EXPECTED              ACTUAL
   --------              ------
   apiVersion: v1        apiVersion: v1
   data:                 data:
X    config.yaml: |-       config.yaml: "null"
X      item1: 1          kind: ConfigMap
X      item2: 2          metadata:
X  kind: ConfigMap         name: issue4905
X  metadata:
X    name: issue4905
    hasgett.go:22: Expected not equal to actual
--- FAIL: TestHelmChartInflationGeneratorIssue4905 (0.24s)
```

Signed-off-by: Kazuki Suda <kazuki.suda@gmail.com>

plugin/builtin/helmchartinflationgenerator/testdata/charts/issue4905/Chart.yaml

@@ -0,0 +1,24 @@
+apiVersion: v2
+name: issue4905
+description: A Helm chart for Kubernetes
+
+# A chart can be either an 'application' or a 'library' chart.
+#
+# Application charts are a collection of templates that can be packaged into versioned archives
+# to be deployed.
+#
+# Library charts provide useful utilities or functions for the chart developer. They're included as
+# a dependency of application charts to inject those utilities and functions into the rendering
+# pipeline. Library charts do not define any templates and therefore cannot be deployed.
+type: application
+
+# This is the chart version. This version number should be incremented each time you make changes
+# to the chart and its templates, including the app version.
+# Versions are expected to follow Semantic Versioning (https://semver.org/)
+version: 0.1.0
+
+# This is the version number of the application being deployed. This version number should be
+# incremented each time you make changes to the application. Versions are not expected to
+# follow Semantic Versioning. They should reflect the version the application is using.
+# It is recommended to use it with quotes.
+appVersion: "1.16.0"

plugin/builtin/helmchartinflationgenerator/testdata/charts/issue4905/templates/_helpers.tpl

@@ -0,0 +1,62 @@
+{{/*
+Expand the name of the chart.
+*/}}
+{{- define "issue4905.name" -}}
+{{- default .Chart.Name .Values.nameOverride | trunc 63 | trimSuffix "-" }}
+{{- end }}
+
+{{/*
+Create a default fully qualified app name.
+We truncate at 63 chars because some Kubernetes name fields are limited to this (by the DNS naming spec).
+If release name contains chart name it will be used as a full name.
+*/}}
+{{- define "issue4905.fullname" -}}
+{{- if .Values.fullnameOverride }}
+{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" }}
+{{- else }}
+{{- $name := default .Chart.Name .Values.nameOverride }}
+{{- if contains $name .Release.Name }}
+{{- .Release.Name | trunc 63 | trimSuffix "-" }}
+{{- else }}
+{{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" }}
+{{- end }}
+{{- end }}
+{{- end }}
+
+{{/*
+Create chart name and version as used by the chart label.
+*/}}
+{{- define "issue4905.chart" -}}
+{{- printf "%s-%s" .Chart.Name .Chart.Version | replace "+" "_" | trunc 63 | trimSuffix "-" }}
+{{- end }}
+
+{{/*
+Common labels
+*/}}
+{{- define "issue4905.labels" -}}
+helm.sh/chart: {{ include "issue4905.chart" . }}
+{{ include "issue4905.selectorLabels" . }}
+{{- if .Chart.AppVersion }}
+app.kubernetes.io/version: {{ .Chart.AppVersion | quote }}
+{{- end }}
+app.kubernetes.io/managed-by: {{ .Release.Service }}
+{{- end }}
+
+{{/*
+Selector labels
+*/}}
+{{- define "issue4905.selectorLabels" -}}
+app.kubernetes.io/name: {{ include "issue4905.name" . }}
+app.kubernetes.io/instance: {{ .Release.Name }}
+{{- end }}
+
+{{/*
+Create the name of the service account to use
+*/}}
+{{- define "issue4905.serviceAccountName" -}}
+{{- if .Values.serviceAccount.create }}
+{{- default (include "issue4905.fullname" .) .Values.serviceAccount.name }}
+{{- else }}
+{{- default "default" .Values.serviceAccount.name }}
+{{- end }}
+{{- end }}

plugin/builtin/helmchartinflationgenerator/testdata/charts/issue4905/templates/configmap.yaml

@@ -0,0 +1,7 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: {{ include "issue4905.fullname" . }}
+data:
+  config.yaml: |-
+    {{- .Values.config | toYaml | nindent 4 }}

plugin/builtin/helmchartinflationgenerator/testdata/charts/issue4905/values.yaml

@@ -0,0 +1 @@
+config: # null