Add tests to verify that crash is fixed elsewhere. Fixes #19328

[raquo]

Adding tests for crash reproduction #19328 that I reported, that was already fixed in nightly.

I added the pos ones just in case, as protection against potential regressions. So far I managed to reproduce the crash only when the implicit was missing, as in neg tests. I can remove the pos tests if you think these are excessive.

I ran only my own tests locally, they passed.

Fixes #19328

cc @soronpo

[som-snytt]

Probably only neg tests are required, as it's incurred by reporting.

But you could add the tiny test for #19022 and get another ticket to your credit.

[raquo]

Ok I removed the pos tests.

Unfortunately I can't reproduce the #19022 crash with Scala 3.3.1. It doesn't crash with the latest scala cli, sbt, or intellij for me. So I doubt that adding the snippet in that ticket as a test would actually trigger the condition that needs testing. The ticket implies that some compiler flags are needed for reproduction, but I'm not sure which ones. I tried -Wconf:v in scala cli, still no crash for me.