Create a generic helper function that finds extra containerd runtimes.
The code was originally inside of the nvidia container discovery file.
Signed-off-by: Flavio Castelli <fcastelli@suse.com>

Discover the containerd shims based on runwasi that are already
available on the node.

The runtimes could have been installed either by a package manager or by
the kwasm operator.
Signed-off-by: Flavio Castelli <fcastelli@suse.com>

The containerd configuration on a Linux system now handles the nvidia
and the WebAssembly runtimes.
Signed-off-by: Flavio Castelli <fcastelli@suse.com>

Added runtime classes for crun/wasm/nvidia
Signed-off-by: Vitor Savian <vitor.savian@suse.com>

Added default runtime flag
Signed-off-by: Vitor Savian <vitor.savian@suse.com>