Explicitly set values have highest priority, then profile settings, then chart defaults.

As an implementation detail of profiles, the default values for the chart are all nested under `defaults`.
When configuring the chart, you should not include this.
That is, `--set some.field=true` should be passed, not `--set defaults.some.field=true`.

### Ambient

  optional string type = 1;

  // Status of the condition, one of True, False, Unknown.
  // Approved, Denied, and Failed conditions may not be "False" or "Unknown".
  // Defaults to "True".
  // If unset, should be treated as "True".
  // +optional
  optional string status = 6;

  // brief reason for the request state
  // +optional
  optional string reason = 2;

  // the default priority for pods that do not have any priority class.
  // Only one PriorityClass can be marked as `globalDefault`. However, if more than
  // one PriorityClasses exists with their `globalDefault` field set to true,
  // the smallest value of such global default PriorityClasses will be used as the default priority.
  // +optional
  optional bool globalDefault = 3;

defaults:
  global:
    # Used to locate istiod.
    istioNamespace: "istio-system"

  base:
    # Validation webhook configuration url
    # For example: https://$remotePilotAddress:15017/validate
    validationURL: ""

  istiodRemote:
    # Sidecar injector mutating webhook configuration url
    # For example: https://$remotePilotAddress:15017/inject
    injectionURL: ""

  // If the Authorizer does not recognized the kind value, the Authorizer should report an error.
  optional string kind = 1;

  // APIGroup holds the API group of the referenced subject.
  // Defaults to "" for ServiceAccount subjects.
  // Defaults to "rbac.authorization.k8s.io" for User and Group subjects.
  // +optional
  optional string apiGroup = 2;

  // Name of the object being referenced.
  optional string name = 3;

import (
	"istio.io/istio/pkg/env"
	"istio.io/istio/pkg/log"
)

const (
	// Location to read istioctl defaults from
	defaultIstioctlConfig = "$HOME/.istioctl/config.yaml"
)

var (
	// IstioConfig is the name of the istioctl config file (if any)
	IstioConfig = env.Register("ISTIOCONFIG", defaultIstioctlConfig,
		"Default values for istioctl flags").Get()

	LoggingOptions = defaultLogOptions()

  // the default priority for pods that do not have any priority class.
  // Only one PriorityClass can be marked as `globalDefault`. However, if more than
  // one PriorityClasses exists with their `globalDefault` field set to true,
  // the smallest value of such global default PriorityClasses will be used as the default priority.
  // +optional
  optional bool globalDefault = 3;

defaults:
  global:

    # ImagePullSecrets for control plane ServiceAccount, list of secrets in the same namespace
    # to use for pulling any images in pods that reference this ServiceAccount.
    # Must be set for any cluster configured with private docker registry.
    imagePullSecrets: []

    # Used to locate istiod.
    istioNamespace: istio-system

    externalIstiod: false
    remotePilotAddress: ""

		//	WantException:  false,
		//},
		{ // case 1
			Args: strings.Split("list", " "),
			ExpectedOutput: `FLAG                    VALUE            FROM
authority                                default
cert-dir                                 default
insecure                                 default
istioNamespace          istio-system     default

1. The builtin values.yaml defaults
2. The profile the user selects
3. Users input (-f or --set)

Unfortunately, Helm provides us (1) and (3) together (as .Values), making it hard to insert (2).

However, we can workaround this by placing all of (1) under a specific key (.Values.defaults).
We can then merge the profile onto the defaults, then the user settings onto that.