Improvements to UUID:
* uuid now works with upper and lowercase
* sped up UUID.String() using stringbuilder, added benchmark
* UUID.String(): grow builder to prevent allocs
* make test in cicd happy
I have intentionally chosen to implement HasServiceUUID() and not
ServiceUUIDs() because returning a slice of UUIDs will likely cause a
heap allocation. And perhaps the most common use may be checking whether
a packet has a particular UUID, so no list is necessary. Getting the
full list can of course be implemented in the future, if needed.