Due to an upcoming change to how the plugins will be instaled on Windows,
they need to be a directory that does _not_ contain `docker-credential-*`.
Therefore, download them into a separate directory instead.

Actual usage will be fixed in follow-up commits.

Signed-off-by: Mark Yen <[email protected]>

The previous commit downloaded the plugins to a different directory; update
the macOS and Linux integration manager to use that directory instead.
Windows will be fixed later.  We still add symlinks to `~/.rd/bin/` so that
if the user runs e.g. `docker-compose` instead of `docker compose`, the
executable will still be found.

Signed-off-by: Mark Yen <[email protected]>

Instead of copying the docker CLI plugins to `~/.docker/cli-plugins`, set
up `~/.docker/config.json` to add the Rancher Desktop docker CLI plugins
directory as an extra directory to scan for plugins.  On Windows, this
appears to take precedence over `~/.docker/cli-plugins`, therefore
resolving issues with not updating the plugins.  For symmetry, also do the
same for WSL distributions.

Signed-off-by: Mark Yen <[email protected]>

Now that we ship the plugins in a separate directory, we also need to add
that directory to $PATH so that if the user wants to call it directly it
can be done.

Signed-off-by: Mark Yen <[email protected]>

The plugins have been moved, so we need to provide a different directory if
they are called for.  This is used to locate `docker-compose` during
extension installation.

Signed-off-by: Mark Yen <[email protected]>

- Exclude docker credential helpers when checking for docker CLI plugins in
  moby client
- Rename various variables
- Other misc fixes

Signed-off-by: Mark Yen <[email protected]>