cluster: moving towards no exceptions

[alyssawilk]

Risk Level: low Testing: updated tests Docs Changes: n/a Release Notes: n/a https://github.com/envoyproxy/envoy-mobile/issues/176

[repokitteh-read-only[bot]]

As a reminder, PRs marked as draft will not be automatically assigned reviewers, or be handled by maintainer-oncall triage.

Please mark your PR as ready when you want it to be reviewed!

:cat:

Caused by: https://github.com/envoyproxy/envoy/pull/34896 was opened by alyssawilk.

see: more, trace.

[alyssawilk]

sorry one more fix - one of the prior PRs caused problems interanlly because the constructor was private and there were internal subclasses. trying to head that off here.

[wbpcode]

ci...