Since the removal of `build.sh`, we don't include any information about
the revision Dendrite was build from. Since go1.18, the revision a
binary was build from is automatically included, so we can try to get
that instead.
This also adds a `dendrite_up` metric showing the current version
(`dendrite_up{version="0.13.1+c796f20"} 1`)
Closes#2993