fix(datadog): RBAC for resources labels/annotations as tags

[jscaltreto]

What this PR does / why we need it:

This fixes two issues with how the chart it rendered when datadog.kubernetesResourcesAnnotationsAsTags and/or datadog.kubernetesResourcesLabelsAsTags are used:

• Keys with more than 1 . were incorrectly rendered, as is frequently used with CRDs.
• When both labels and annotations are specified, the labels map is merged into DD_KUBERNETES_RESOURCES_ANNOTATIONS_AS_TAGS

Which issue this PR fixes

• fixes Resources labels/annotations as tags renders invalid RBAC rules #1684

Special notes for your reviewer:

I verified the fix using helm template and the following values:

datadog:
  kubernetesResourcesAnnotationsAsTags:
    pods:
      some-annotation: "some-value"
    deployments.apps:
      another-annotation: "another-value"
    customs.example.com:
      custom-annotation: "custom-value"
  kubernetesResourcesLabelsAsTags:
    services:
      some-label: "some-value"
    statefulsets.apps:
      another-label: "another-value"
    anotercustoms.example.com:
      custom-label: "custom-value"

The RBAC rules were correctly rendered as:

rules:

# Iterate through the apiGroups and create rules for each resource
- apiGroups:
  - ""
  resources:
  - pods
  - services
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - "apps"
  resources:
  - deployments
  - statefulsets
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - "example.com"
  resources:
  - anotercustoms
  - customs
  verbs:
  - get
  - list
  - watch

And the cluster-agent env vars are correct:

- name: DD_KUBERNETES_RESOURCES_LABELS_AS_TAGS
  value: '{"anotercustoms.example.com":{"custom-label":"custom-value"},"services":{"some-label":"some-value"},"statefulsets.apps":{"another-label":"another-value"}}'
- name: DD_KUBERNETES_RESOURCES_ANNOTATIONS_AS_TAGS
  value: '{"customs.example.com":{"custom-annotation":"custom-value"},"deployments.apps":{"another-annotation":"another-value"},"pods":{"some-annotation":"some-value"}}'

Checklist

• Chart Version bumped
• Documentation has been updated with helm-docs (run: .github/helm-docs.sh)
• CHANGELOG.md has been updated