Add '~' and '^' to the supported characters for the field. These
characters are needed to be able to define all versions that are
compatible with the UAPI Version Format specification.
One example where this is used is the `%A` flag in systemd.unit. If we
don't allow these other characters, we for example cannot declare a
pre-relase version.
systemd, as far as I can tell, doesn't enforce any restrictions on the
os-release fields.
https://uapi-group.org/specifications/specs/version_format_specification/
ff776981fe