Fix broken tests

[kayceesrk]

Here are the currently failing tests:

• [ ] tests/asmcomp/fib
• [ ] tests/asmcomp/tak
• [ ] tests/asmcomp/quicksort
• [ ] tests/asmcomp/quicksort2
• [ ] tests/asmcomp/soli
• [ ] tests/asmcomp/tagged-fib
• [ ] tests/asmcomp/tagged-integr
• [ ] tests/asmcomp/tagged-quicksort
• [ ] tests/asmcomp/tagged-tak
• [ ] tests/backtrace/backtrace.ml
• [ ] tests/backtrace/backtrace.ml
• [ ] tests/backtrace/backtrace.ml
• [ ] tests/backtrace/backtrace.ml
• [ ] tests/backtrace/backtrace2.ml
• [ ] tests/backtrace/raw_backtrace.ml
• [ ] tests/backtrace/backtrace_deprecated.ml
• [ ] tests/backtrace/backtrace_slots.ml
• [x] tests/lib-threads/testsieve.ml
• [x] tests/lib-threads/torture.ml
• [ ] tests/runtime-errors/stackoverflow.native
• [ ] tests/tool-debugger/basic/
• [ ] tests/tool-debugger/no_debug_event/
• [ ] tests/typing-extensions/extensions.ml.reference

The failing tests can be put into 3 broad classes

1. asmcomp -- These tests just need to be updated to reflect the changes to the native backend
2. threads -- Fix sys-threads and vm-threads
3. backtrace -- Fix the backtrace support

[kayceesrk]

Threads tests have been fixed by https://github.com/ocamllabs/ocaml-effects/commit/47a2fcbcefe21e2e73929acf5beb9a91780940ef.