Timedeltas: Understand µs
- [ ] closes #xxxx
- [X] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [X] whatsnew entry


These are emitted by golangs `time.Duration` printing: https://github.com/golang/go/blob/36b815edd6cd23d5aabdb488c24db2033bbdeea2/src/time/time.go#L669
> pls add a test & a what’s new note (other enhancements)

Done

> is this fixing a specific issue?

Yes, this is fixing the "Pandas can not parse golang duration strings if they contain microseconds" issue. what i mean is do we already have an open issue for what this is fixing? > what i mean is do we already have an open issue for what this is fixing?

No, want me to open one and add a closes directive to the PR? @jreback The `CI / Checks (pull_request)` failed with a `HTTPError: HTTP Error 503: Backend fetch failed`. That's not from the PRs changes I guess? Can you restart it or do I need to force push? no don’t open an issue @alvaroaleman Can you please rebase? the CI is failing due to an issue we recently resolved, merging master should solve this. @MomIsBestFriend done, all checks are green now :) thanks @alvaroaleman 