We already have "kernel" and "base" and plugins also follow this
pattern by only registering its name once per devel or release
version. This kills ambiguity for "opnsense" vs. "opnsense-version"
and makes it more branding friendly. Suffice to say "core", "kernel"
and "base" are reserved names and also align with tools.git.
Now that we have metadata injection at build time read it instead
of its auxiliary files. Allow live-mount to snoop the metadata and
afterwards we can start to marry the version and firmware-product
file.
Last puzzle piece will be a tool called "opnsense-version" to read
the JSON metadata and return it in a piecemeal fashion of a part
of the system requires that info, especially from the shell.
