Per-test timeouts accepted for cmd/go

The accepted proposal to add per-test timeouts to cmd/go is the one to note: the existing binary-wide timeout has never been much use when a single case wedges, and this finally gives `go test` a way to bound individual cases. Elsewhere there is a separate proposal to deprecate the testing package's exposed internals, which suggests the testing surface is getting a broader think. On the lighter side, someone stood up a shared 200x60 SSH canvas built with Charm's wish and bubbletea, which is a pleasingly silly use of a terminal.