[Resource] remove class and namespace export

[dyladan]

Remove the Resource class from the exports of @opentelemetry/resource making it purely an implementation detail. This will include exporting top-level functions and types for interacting with resource objects.

[trentm]

The intent here is that this usage: https://opentelemetry.io/docs/languages/js/resources/#adding-resources-in-code
would change to the user passing in a plain old JS object for the resource attributes? E.g.:

const sdk = new opentelemetry.NodeSDK({
  resource: {
    [ ATTR_SERVICE_NAME ]: "yourServiceName",
    [ ATTR_SERVICE_VERSION ]: "1.0",
  }
});

?

Or, perhaps something that includes "attributes" to prepare for future entity-related things?

const sdk = new opentelemetry.NodeSDK({
  resourceAttributes: {
    [ ATTR_SERVICE_NAME ]: "yourServiceName",
    [ ATTR_SERVICE_VERSION ]: "1.0",
  }
});