fix service race condition

[noah-wardlow]

• Allow re-advertisement: advertise() and
  advertiseAsync() now automatically unadvertise before
  re-advertising instead of throwing errors
• Make unadvertise idempotent: unadvertise() now
  safely returns instead of throwing when called on
  non-advertised services
• Fix cleanup order: Callbacks are removed before
  marking as unadvertised to prevent processing
  requests during cleanup

[EzraBrooks]

Firstly I think we should make this PR upstream

But secondly I think this might be too fragile. I added those throws because before they were there this failed silently due to race conditions, so I made it fail hard instead.

This whole library is built around eventemitters - is there some way we can debounce, queue, throttle, or otherwise lock the advertisement to ensure no race conditions can occur here?

[noah-wardlow]

RobotWebTools#919