RFC: validate that only a single instance of ServiceLifecycle is created per process

[tomerd]

motivation: having multiple instance of ServiceLifecycle generally points to a mistake, which we can help validate

changes: add check in init to validate single instance

alternatively, we may be less rigid, we can move this check to start so multiple instance may be created, but only one started - I think I prefer this option

[fabianfett]

@tomerd Wanna go forward with this PR?

[FranzBusch]

Going to close this now since our new APIs don't have that restriction.