Report causes of errors

Change errors in log messages to be properly reported, with causes. This is the global whack-a-mole implied by the new facility in !936 (merged).

Fixes #680 (closed)

Specifically, I grepped the whole codebase for info!, warn! and error!. I eyeballed the call and when the message was an error (according to my interpretation of the variable name), I arranged to call ErrorReport::report(), which prints the causes.

In some places errors were logged using {:?} which is a plausible way to try to print causes in the absence of an error reporter. I replaced those with {} and .report(), too.

In some places, the error was anyhow::Error, which doesn't itself implement std::error::Error, so there we must wrap it up in tor_error::Report. (This discrepancy is annoying, and maybe there is a better way; two extension traits both providing .report() maybe.)

I fixed a couple of actually-wrong errors that I noticed.

I have not checked anything at debug! or lower. Nor have I checked that the log messages make semantic sense. I have not tested this, either, but I did test the pattern in !936 (merged). We already audited the errors in our codebase for sensitive data in their causes, so I think always reporting causes is correct from a safelogging point of view. I found and fixed one exception to this, where we were logging an error type from a dependency (in the DNS proxy code).