A caller that applies a mount transform itself had to say so by naming the
mount type "format/*", a sentinel the mount manager constructs internally
by concatenating a transform name with "/*". Both sides had to
independently know and agree on that convention, and the resulting string
is neither a mount type nor a transform name.
Add AllowTransforms, and WithAllowTransform to set it, so a transform can
be claimed by its own name instead. The "/*" convention is removed rather
than kept as a second accepted spelling: it existed only to be produced by
the runtime-allow-mounts annotation, which is removed in an earlier commit
in this series, and there is no other producer of it in this tree.
Signed-off-by: Derek McGowan <derek@mcg.dev>
