Log more lines for exceptions

What does this MR do?

Gitlab::BacktraceCleaner excludes some 'boring' lines from exception stack traces: initializers, middlewares, logging code, etc.

This makes sense for development usage, or where we want to trace the origin of (say) a database query. But in logs - particularly production logs - we want all of our application code in the stack trace, because we might have an error in our middleware, or we might be in a particular code path triggered by a middleware.

(As it happens, we can't actually log errors from middlewares anyway: #227373. But we probably shouldn't exacerbate that problem!)

MR inspired by gitlab-org/charts/gitlab#2098 (comment 396933521).