Disable redaction when tests are running

[squarejesse]

This is not particularly helpful:

Expected: `UiResult{form_blocker=██}
Actual:   `UiResult{form_blocker=██}

It’d be rad if we could detect that we’re running in test, and disable redaction in that case.

Somehow.

[oldergod]

I think detecting that we are in a test can be done for Gradle or Junit. I'm not sure then how to change redacted field printing though...

[JakeWharton]

Seems pretty risky. Would think doing a fun <T : Message<*, *>> assertThat(message: T): Assert<T> that ended up using a non-redacted string representation on failure would be safer.