[UI] Better error message on missing user-gcp-sa

[Bobgy]

/area frontend
/kind feature

Problem

There have been a few community questions raised about confusion in user-gcp-sa change, because typically pipeline authors may be ml experts, but don't have enough about kubernetes to debug the user-gcp-sa secret issue by themselves.

Also when the secret is missing, the pipeline will be stalled in Pending state with zero information on KFP UI.

Proposed Solution

Therefore, I'm thinking about if we can detect this error in KFP UI and show a link to related documentation directly, so that they get the direction right away.

Related Context

#1691 (comment)
#2589

/cc @amygdala