Better handling of errors when using the tracing tool in snuba-admin

[phacops]

When using the tracing tool, queries can return an error. Right now, it's either returned in a JavaScript alerts or not returned at all and we frequently have to open the developer tools of our browser to reach for the failed HTTP request body and actually look at the error that was returned.

We should surface the error in a better way than JavaScript alerts and make sure they are displayed every time, whether it's a ClickHouse error message or an HTTP failure due to a timeout.