Instead of a plugin `version` subcommand that responds with a string
(established in #24497), respond to a `fingerprint` command with a data
structure that we may extend in the future (such as plugin capabilities,
like size constraint support?). In the immediate term, it's still just the
version: `{"version": "0.0.1"}`
In addition to leaving the door open for future expansion, I think it will
also avoid false positives detecting executables that just happen to
respond to a `version` command.
This also reverses the ordering of the fingerprint string parts
from `plugins.host_volume.version.mkdir` (which aligned with CNI)
to `plugins.host_volume.mkdir.version` (makes more sense to me)
af967184a6