Improve GQL types generation on upload sizes

[tyteen4a03]

Currently, the GQL type generator generates something like this:

type Media_Sizes {
  thumbnail: Media_Sizes_Thumbnail
  og: Media_Sizes_Og
  blogText: Media_Sizes_BlogText
  blogLightboxSmall: Media_Sizes_BlogLightboxSmall
  blogLightboxMedium: Media_Sizes_BlogLightboxMedium
}

type Media_Sizes_Thumbnail {
  url: String
  width: Float
  height: Float
  mimeType: String
  filesize: Float
  filename: String
}

type Media_Sizes_Og {
  url: String
  width: Float
  height: Float
  mimeType: String
  filesize: Float
  filename: String
}

type Media_Sizes_BlogText {
  url: String
  width: Float
  height: Float
  mimeType: String
  filesize: Float
  filename: String
}

type Media_Sizes_BlogLightboxSmall {
  url: String
  width: Float
  height: Float
  mimeType: String
  filesize: Float
  filename: String
}

type Media_Sizes_BlogLightboxMedium {
  url: String
  width: Float
  height: Float
  mimeType: String
  filesize: Float
  filename: String
}

As the types are the same, it would be great to consolidate them into one type so we can use Fragments on them.