Support "resource()" function to get a existing resource reference in one line/as a property value

[alex-frankel]

Related to #1722

Something like:

param parentResourceName

resource foo 'my.rp/parent/child' = {
  parent: resource('my.rp/parent', parentResourceName)
}

Should also support a full resourceId

param parentResourceId string

resource foo 'my.rp/parent/child' = {
  parent: resource(parentResourceId)
}

[anthony-c-martin]

Duplicate of #2245