Hook TB2->stream_end() into something

[schwern]

Right now, nothing calls the TB2->stream_end event. You have to call it manually.

It should be called by done_testing().

It should probably be called on DESTROY, configurable, and only if the stream started.

[schwern]

DESTROY is a no go. It appears that during global destruction we can't rely on orderly destruction and bits of TB2 are missing by the time it happens.

At the moment it's done in an END block by TB2::Module on the singleton. That seems sensible as in other situations you'll have access to the object itself.

It still may be useful to put it in TB2->DESTROY but I'll wait until there's a use case.