Deriving clauses of `Ptr` are not calculated correctly

[endgame]

In amazonka-emr-containers, there is the following set of mutually-recursive shapes:

• Configuration contains ConfigurationList and a Sensitive field.
• ConfigurationList contains Configuration

Under #862 , the map of shapes was populated in such a way that ConfigurationList held a Ptr to Configuration, which meant that it generated a deriving clause containing a static set of class names, including Read. This fails to compile, as Configuration contains a Sensitive field, and so cannot have a Read instance.

The correct fix is to determine the set of deriving clauses by constraint solving — https://github.com/endgame/amazonka/commit/bdcba74b64d536d303be99cf9ecdd781766c770d was an attempt at this, but I am abandoning it after a week and a half because it's still broken. Supporting #872 will require a serious re-architecting of the generator anyway, so let's do it properly:

• [X] Build out a botocore library which is a direct representation of the data files provided by AWS - service, paginators, waiters, and the new endpoint-rule-set type.
• [ ] Add some sort of "JSON deep-merge" functionality to botocore to support the splicing in of annexes.
• [ ] Rewrite the generator to read from botocore types
• [ ] Rewrite the generator to use botocore, and differentiate each stage (classifying shapes; applying renames/overrides; generating code)
• [ ] Consider a more modern lib than haskell-src-exts for code generation (maybe ghc-exactprint?)
• [ ] Kill the cofree comonad of shapes once and for all. it was a defensible idea when the inclusion graph of shape definitions was a DAG, but that has not been true for a very long time. If every shape reference is handled as if it were a Ptr by looking it up in a MonadReader context, edge cases like this will stop happening.