Explore getting rid of is_type and as_type

[bdemann]

I think that the is_type and as_type (eg is_array or as_primitive) was only needed back when we were making a global list of all of the types. We might not need it anymore. Probably after the kybra and azle refactor is done we can assess that and take action at that point.

Ask dan if he uses this as all in azle, see if we use it in kybra, if not, get rid of them, if so, see if we actually need them repeat