This PR fixes an issue where go-to-definition would jump to the wrong
location in presence of async theorems.
While the elaborator does not explicitly depend on `FVar`s not being
reused between declarations, the language server turned out to do so. As
we would have to split the name generator in any case as soon as we add
any parallelism within proofs, we now do so for any async code in order
to uphold this invariant again.
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Co-authored-by: mhuisi <mhuisi@protonmail.com>
Asynchronous elaboration means that constants can exist in the elab
environment while failing to be added to the kernel environment, avoid
the latter by falling back to axioms there
