Add support for record type data

[mtoy-googly-moogly]

I started just trying to do support for records per: WN-0015

But It was constantly difficult to reason about the code because tech debt in the compiler.

So this is MOSTLY refactoring StructDef to more clearly and concisely describe the structures which are being defined.

... and record support

... and a lot of the work for array support

... and refactored table and sql schema fetching to eliminate the copy-pasted-in-every-dialect schema cache.

... and other cleanup because i touched a lot of code and i tried to make everything i touched better.

.. and some documentation for StructDef and FieldDef