Nospecialize close(c::Channel, excp::Exception) on excp. (#49508)
* Nospecialize close(c::Channel, excp::Exception) on excp.
Fixes https://github.com/JuliaLang/julia/issues/49507.
Avoids dynamic dispatch when closing a Channel with an Exception, and
should avoid a call into the runtime for julia compilation when
attempting to report an exception.
* Add test for this case.
