Remove physical types

[jacques-n]

For people who need variations, they can use user defined extension types. (Simpler is better)

This is based on this subthread

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This change is 

[emkornfield]

I think the issue before is two items are conflated

1. Memory Layout - how a particular type is laid out in memory. I would guess plans can be agnostic to exact representation.
2. Logical Encodings - On the surface I think I agree with your assertion from the thread that having this modeled is likely important.

So I think this change is fine, but we might want to revisit point #2.

[jacques-n]

Abandoning. Going with #25