pvsecret: Add -i -o option variants

All pvattest subcommands use the command line option -i <input> and -o
<output> to specify file input and output respectively. pvsecret however
uses mostly positional arguments for <input> and <output> exclusively,
e.g. pvattest check input.bin output.yaml

$ pvsecret add secret.bin

This provides an inconsistent user interface within the Secure
Execution tools and may confuse users.

Add the -i and -o option to the subcommands if applicable.
Input/output can then be specified like so:

$ pvsecret add -i secret.bin
$ pvsecret list -o list.yaml
$ pvsecret verify -i FILE -o out.yaml
$ pvsecret retrieve -i ID -o id.yaml

Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

rust/pvsecret/src/cmd/create.rs

@@ -322,7 +322,7 @@ fn write_yaml<P: AsRef<Path>>(
     write_out(&yaml_path, secret_info, "secret information")?;
     warn!(
         "Successfully wrote secret info to '{}'",
-        yaml_path.display().to_string()
+        yaml_path.display()
     );
     Ok(())
 }