Move error handling to C code (#265)

* move error handling to C code

* add error test

* fix TestErrorAllocs

* undo version loading

* fix TestErrorMultithread

* autogenerate mkcgoNoEscape

* add nosplit

* Apply suggestions from code review

Co-authored-by: Davis Goodin <[email protected]>

* decouple error implementation

* improve go_hash_sum error messages

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Co-authored-by: Davis Goodin <[email protected]>

Author: qmuntal