Debugging info is needed for error messages, and for
lowering. For the former, we need debug info inside
tracers. For the latter, inside Jaxprs. We add a
new set of tests that intentionally leak tracers while
tracing and then we check that the tracers have the
expected debug info. We also form Jaxprs and we
check that they have the expected debug info.
We uncovered a few missing debug infos, those are
marked with TODO.
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