Replace ./scripts/install_tool.sh with `gobin`, such that we have
consistent handling for all tools needed for build and consistent
versioning within ./tools/mod/go.mod.
Side changes:
- Expose /scripts/fix.sh that fixes formatting and bom across modules
- Expose *.sh variants of scripts like build and ./test (first step
towards replacement).
- Make stderr output of commands explicit and make commands use
different color than callouts.
Piotr Tabor