Proposal floats testing.FullPath() to expose -fullpath to tests

A new proposal would add testing.FullPath() alongside the existing Short and Verbose helpers, letting tests that report paths honour the -fullpath flag instead of guessing. A separate, smaller cleanup proposes deprecating debug/pe.ImportDirectory, which has apparently been unusable for the fifteen years it has existed. Elsewhere, a TypeScript developer missed if err != nil badly enough to build an errval package for it, which is one way to pay tribute.