"customizations" (and legacy extension, settings properties) not processed in features

[Chuxel]

Running devcontainer read-configuration --include-features-configuration on a workspace with a devcontainer.json with features does not return customizations or the legacy extensions or settings properties (whether original or converted).

In the latest Remote - Containers release extensions are not installed and settings are not applied either.

They seem to be missing in several spots along with other properties from the spec (https://github.com/devcontainers/spec/blob/main/proposals/devcontainer-features.md#devcontainer-featurejson-properties).

Possible places where the issue could be coming from (if not all of them):

• cli/src/spec-configuration/containerFeaturesConfiguration.ts

  Lines 931 to 940 in 0147a36

  	feature.containerEnv = featureJson.containerEnv;
  	feature.buildArg = featureJson.buildArg;
  	feature.options = featureJson.options;
  	feature.installAfter = featureJson.installAfter;
  	feature.init = featureJson.init;
  	feature.privileged = featureJson.privileged;
  	feature.capAdd = featureJson.capAdd;
  	feature.securityOpt = featureJson.securityOpt;
  	feature.mounts = featureJson.mounts;
  	feature.entrypoint = featureJson.entrypoint;

• cli/src/spec-configuration/containerFeaturesConfiguration.ts

  Lines 964 to 971 in 0147a36

  	feature.buildArg = seekedFeature?.buildArg;
  	feature.options = seekedFeature?.options;
  	feature.init = seekedFeature?.init;
  	feature.privileged = seekedFeature?.privileged;
  	feature.capAdd = seekedFeature?.capAdd;
  	feature.securityOpt = seekedFeature?.securityOpt;
  	feature.mounts = seekedFeature?.mounts;
  	feature.entrypoint = seekedFeature?.entrypoint;

• cli/src/spec-configuration/containerFeaturesConfiguration.ts

  Lines 24 to 48 in c97190e

  	export interface Feature {
  	id: string;
  	version?: string;
  	name: string;
  	description?: string;
  	cachePath?: string;
  	internalVersion?: string; // set programmatically
  	consecutiveId?: string;
  	documentationURL?: string;
  	licenseURL?: string;
  	options?: Record<string, FeatureOption>;
  	buildArg?: string; // old properties for temporary compatibility
  	containerEnv?: Record<string, string>;
  	mounts?: Mount[];
  	init?: boolean;
  	privileged?: boolean;
  	capAdd?: string[];
  	securityOpt?: string[];
  	entrypoint?: string;
  	installAfter?: string[];
  	include?: string[];
  	exclude?: string[];
  	value: boolean | string | Record<string, boolean | string | undefined>; // set programmatically
  	included: boolean; // set programmatically
  	}

[Chuxel]

//cc @chrmarti @alexdima @bamurtaugh given the Remote - Containers impact.