Make it more obvious when flake evaluations fail

[raboof]

The hourly import currently succeeds even when there's individual flakes that failed. The PR validation does fail when any fails.

We should probably make the import job run to completion when one flake fails, but then fail with a clear report/issue, so we notice when flakes stop working, rather than only noticing when an unrelated PR fails

[dyegoaurelio]

We could have a pinned issue where each action run would edit with a report,

kind of like zed-industries/zed#6952 .

Would be nice if we could also have some information regarding the result for flakes that didn't fail as well.

e.g:
When working on #1092 I noticed that some of the already added flakes aren't yielding any package. It's also not easy to spot issues like these currently.