Description

Our prepare script is currently embedded in our evergreen yml. Pulling it out makes running it locally and on spawn hosts much easier.

Additionally, while attempting pulling out this script it was discovered one of our tasks is failing a lot of tests but reporting success (NODE-4642). It turns out errors thrown from mocha reporters are squashed (visually) but still exit the process, but with success. It's a small change to add error handling to our reporter.

While we're adding error handling to the reporter we should remove stdout/err capturing. We don't use it, and it doesn't correctly work on evergreen, and it make xunit.xml huge.