cmd/go: fix: tolerate type errors in dependencies #81862

The analysis framework is robust to build errors, and robust analyzers can opt to be run even on packages that are not transitively error-free. However, the driver logic in go vet/fix does not run analysis actions if any dependency had errors. Consequently, go fix cannot be conveniently used to fix breakage spread across a project in one go, because it will need to be run iteratively over successive frontiers of broken dependencies.

We should change the go vet/fix driver so that, like gopls, type errors are no obstacle to running analysis, obtaining diagnostics, and applying fixes.

(Loosely related: #77482)