**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
Add `goleak` to detect leaks in tests. Leaking goroutines were detected
that were caused by a dependency that we can ignore
(`go.opencensus.io/stats/view.(*worker).start`), some `Shutdown` calls
were also added that were missing.
**Link to tracking Issue:** <Issue number if applicable>
#9165
**Testing:** <Describe what testing was performed and which tests were
added.>
Added check is passing as well as existing tests.