[test] Add coverage for throwing custom "use cache" cache handler (#95984)
This is relevant if the cache is in a broken state or the keys or
entries are not suitable (e.g. an entry that's to large to be stored).
Revealed several oddities:
1. cache handler have no no sources content (not too bad since that
means the codeframe points into the problem `use cache` function which
is usually the cause)
2. A throwing `set` is swallowed in dev
3. A throwing `get` is logged as a caught error and an unhandled
rejection. This is spammy.