bug#45402: Rename Tramp method "media"

[Drew Adams]

It's no doubt too late now, at least in general,
but maybe it would make sense to use a prefix
for Tramp, kind of like what we do for libraries.

Besides being too late, I imagine someone will
say that that would be too verbose for users to
type, which is true.

But even a prefix of "t" might be sufficient to
usually distinguish Tramp's protocol names.  In
this case, ~//tmedia would mean Tramp's protocol
and ~//media would mean (change to) local
directory /media.

Yeah, it's ugly.  But the Tramp syntax is
apparently inherently ambiguous here (i.e., can
conflict with a dir name).