Make code-review bot complain loudly if a lint task does not produce a `mozlint.json`

[ncalexan]

In Bug 1956871, I'm trying to ensure that developers don't get surprised by failing lint tasks that aren't surfaced in Phab. That particular issue is due to the in-tree configuration of the linter, but the code-review bot does not help: it should complain that the lint task has not provided the required mozlint.json output rather than ignoring it. Can we do that?

[ahal]

It's not quite this simple, only actual mozlint tasks are expected to provide a mozlint.json file:

code-review/bot/code_review_bot/workflow.py

Line 649 in 357a657

elif name.startswith("source-test-mozlint-"):

I assume that if a task that started with source-test-mozlint failed to provide a mozlint.json, there would be an error as expected (so I think this issue can likely be closed, but I'll leave that up to reviewbot maintainers).

For bug 1956871, I think it comes down to one of two options:

1. Either integrate the tasks into mozlint which includes moving the task definitions into taskcluster/kinds/source-test/mozlint.yml, and get mozlint.json for free
2. Create a custom integration for these tasks in reviewbot, which involves creating a new file like:
   https://github.com/mozilla/code-review/blob/master/bot/code_review_bot/tasks/clang_tidy.py (and use whatever artifact format you desire)