Report thread sanitizer warnings as PR comments

### Description

The thread sanitizer test job has a lot of problems, so causes more trouble for PRs that don't wind up needing it compared to the relatively small amount of issues it's found over time.

We decided to make it nonfailable for this reason in https://github.com/getsentry/sentry-cocoa/pull/3303.

We need subsequent work to grep the logs for any thread sanitizer warnings (see that PR's description for an example of the format) and report them as comments on the PR, ideally on the line of code in the diff reported by the thread sanitizer.