Rework CRD generation to add docs and kubectl explain support

[brandond]

• Convert CRD generation to controller-gen
• Add CRD docs

Example of docs available via kubectl explain:

brandond@dev01:~$ kubectl explain helmchart.spec
GROUP:      helm.cattle.io
KIND:       HelmChart
VERSION:    v1

FIELD: spec <Object>


DESCRIPTION:
    HelmChartSpec represents the user-configurable details for installation and
    upgrade of a Helm chart release.

FIELDS:
  authPassCredentials	<boolean>
    Pass Basic auth credentials to all domains.
    Helm CLI positional argument/flag: `--pass-credentials`

  authSecret	<Object>
    Reference to Secret of type kubernetes.io/basic-auth holding Basic auth
    credentials for the Chart repo.

  backOffLimit	<integer>
    Specify the number of retries before considering the helm job failed.

  bootstrap	<boolean>
    Set to True if this chart is needed to bootstrap the cluster (Cloud
    Controller Manager, CNI, etc)

  chart	<string>
    Helm Chart name in repository, or complete HTTPS URL to chart archive (.tgz)
    Helm CLI positional argument/flag: `CHART`

  chartContent	<string>
    Base64-encoded chart archive .tgz; overides `.spec.chart` and
    `.spec.version`
    Helm CLI positional argument/flag: `CHART`

  createNamespace	<boolean>
    Create target namespace if not present.
    Helm CLI positional argument/flag: `--create-namespace`

  dockerRegistrySecret	<Object>
    Reference to Secret of type kubernetes.io/dockerconfigjson holding Docker
    auth credentials for the OCI-based registry acting as the Chart repo.

  failurePolicy	<string>
  enum: abort, reinstall
    Configures handling of failed chart installation or upgrades.
    - `reinstall` will perform a clean uninstall and reinstall of the chart.
    - `abort` will take no action and leave the chart in a failed state so that
    the administrator can manually resolve the error.

  helmVersion	<string>
    DEPRECATED. Helm version to use. Only v3 is currently supported.

  insecureSkipTLSVerify	<boolean>
    Skip TLS certificate checks for the chart download.
    Helm CLI positional argument/flag: `--insecure-skip-tls-verify`

  jobImage	<string>
    Specify the image to use for tht helm job pod when installing or upgrading
    the helm chart.

  plainHTTP	<boolean>
    Use insecure HTTP connections for the chart download.
    Helm CLI positional argument/flag: `--plain-http`

  podSecurityContext	<Object>
    Custom PodSecurityContext for the helm job pod.

  repo	<string>
    Helm Chart repository URL.
    Helm CLI positional argument/flag: `--repo`

  repoCA	<string>
    Verify certificates of HTTPS-enabled servers using this CA bundle. Should be
    a string containing one or more PEM-encoded CA Certificates.
    Helm CLI positional argument/flag: `--ca-file`

  repoCAConfigMap	<Object>
    Reference to a ConfigMap containing CA Certificates to be be trusted by
    Helm. Can be used along with or instead of `.spec.repoCA`
    Helm CLI positional argument/flag: `--ca-file`

  securityContext	<Object>
    custom SecurityContext for the helm job pod.

  set	<map[string]Object>
    Override simple Chart values. These take precedence over options set via
    valuesContent.
    Helm CLI positional argument/flag: `--set`, `--set-string`

  targetNamespace	<string>
    Helm Chart target namespace.
    Helm CLI positional argument/flag: `--namespace`

  timeout	<string>
    Timeout for Helm operations.
    Helm CLI positional argument/flag: `--timeout`

  valuesContent	<string>
    Override complex Chart values via inline YAML content.
    Helm CLI positional argument/flag: `--values`

  valuesSecrets	<[]Object>
    Override complex Chart values via references to external Secrets.
    Helm CLI positional argument/flag: `--values`

  version	<string>
    Helm Chart version. Only used when installing from repository; ignored when
    .spec.chart or .spec.chartContent is used to install a specific chart
    archive.
    Helm CLI positional argument/flag: `--version`