win,build: try multiple timeservers when signing

Can't get any release builds done right now because globalsign's timeserver isn't responding properly for Authenticode signing requests on Windows!

This PR adds a new file, tools/sign.bat, to do the signing, it tries each of the big available timeservers (globalsign, comodo, verisign, starfield) until it finds one that it can actually use.

Looking for a very speedy review so I can land this and backport to v6, v4, v0.12 and v0.10 and get these releases built! It does work but I've had to make a couple of tweaks while testing. Final testing build should be ready soon in download/release/test/

/cc @nodejs/build @nodejs/platform-windows