Dump junit xml

[dandavison]

Closes #1633

As in temporalio/sdk-python#617 and temporalio/cli#650, I propose to modify the test suite to output junit XML. The motivation for this is that, given appropriate tools, it will make it easier for us to study patterns of flakiness, test timings etc, across matrix builds within a run, and across runs. Producing the files now will allow us to test tools for doing this.

[dandavison]

All changes to go.mod and go.sum are the result of running go get gotest.tools/gotestsum (looks like it was already a transitive dependency IIUC).

[dandavison]

@Quinn-With-Two-Ns To output junit XML I had to switch to using gotestsum. One question here is are you OK with the new test output format from gotestsum? From a quick look it appears that one big difference is that output from successful tests is hidden by default. I was optimistic that we'd be OK with this switch since https://github.com/temporalio/temporal uses it, and it looks like it's quite configurable, and fairly widely used by high profile Go projects: https://github.com/gotestyourself/gotestsum

[Quinn-With-Two-Ns]

No concern about the test format. Question about the general PR though, from the issue it says

The motivation for this is that, given appropriate tools, it will make it easier for us to study patterns of flakiness

Does that appropriate tool exist yet today?

[dandavison]

Does that appropriate tool exist yet today?

Good question. I couldn't find something that would work well, e.g. correlating tests across our matrix builds, so I've started creating our own from scratch. I'm not quite ready to have others test it (but absolutely welcome any help developing it).