feat: make L2 interfaces extend I[ResourceName]Ref

[otaviomacedo]

First batch of L2 interfaces that extend the new I[ResourceName]Ref interfaces. Example:

export interface IDomainName extends IResource, IDomainNameRef {

The goal is to allow classes that now only consume L2 resources, to consume both L1 or L2 via this new interface. Continuing with the example, this is what ApiMappingProps looks like:

export interface ApiMappingProps {
  ...
  /**
   * custom domain name of the mapping target
   */
  readonly domainName: IDomainName; // <-- L2 interface
  ...
}

At the moment, ApiMappingProps.domainName can only be an L2. This change will allow us to make ApiMappingProps more generic:

export interface ApiMappingProps {
  ...
  /**
   * custom domain name of the mapping target
   */
  readonly domainName: IDomainNameRef;
  ...
}

const dn = new CfnDomainName(stack, 'DomainName', {
  domainName,
});

new ApiMapping(stack, 'Mapping', {
  // More generic: we can still use an L2, but also an L1, as in this case, 
  // since CfnDomainName also extends IDomainNameRef
  domainName: dn, 

  api,
  stage: beta,
  apiMappingKey: 'beta',
});

---

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