Revert "Thread safety analysis: Support copy-elided production of scoped...

Revert "Thread safety analysis: Support copy-elided production of scoped capabilities through arbitrary calls"

This caused false positives, see comment on the code review.

> When support for copy elision was initially added in e97654b2, it
> was taking attributes from a constructor call, although that constructor
> call is actually not involved. It seems more natural to use attributes
> on the function returning the scoped capability, which is where it's
> actually coming from. This would also support a number of interesting
> use cases, like producing different scope kinds without the need for tag
> types, or producing scopes from a private mutex.
>
> Changing the behavior was surprisingly difficult: we were not handling
> CXXConstructorExpr calls like regular calls but instead handled them
> through the DeclStmt they're contained in. This was based on the
> assumption that constructors are basically only called in variable
> declarations (not true because of temporaries), and that variable
> decla...