Create 'bsmain' (for bugsink-main) app to hold commands

As had been noted on some of the commands, 'ingest' was not the best place for
them.  However, [project-level apps are not supported in
Django](https://forum.djangoproject.com/t/allow-project-to-have-management-commands/5220/2)
So just create a 'main' app. I want to qualify it as 'myproject-main' though, to avoid
further unqualified global namespace pollution. And I want to avoid prefixing with 'bugsink'
b/c that's annoying for tab-completion. So 'bs' it is.

I've moved all commands over; even though a case could be made that the "feeding" commands
(raise_exception, send_json, stress_test) are somewhat related to ingestion, that's not
a very good case :-)

pyproject.toml

@@ -39,6 +39,7 @@ where = ["."]
 include = [
     "alerts*",
     "api*",
+    "bsmain*",
     "bugsink*",
     "compat*",
     "events*",