[#215] `withWTPInstr_` should throw error exactly on the bad type

Description

Problem: withWTPInstr_ when used with container type, does not point directly to uncomparable key type. For example, when it is used with big_map unit nat it will point to the whole container type as not comparable, instead of just unit is not comparable.

Solution: Update getWTP to report bad type T when typechecking on container type that has incomparable key type.

Related issue(s)

Resolves #215 (closed)

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