rust: Improve code formatting

Do some formatting that are in experimental stage but improve the code
readability.

Use rustfmt with a nightly toolchain and enable:

format_code_in_doc_comments = true
reorder_impl_items = true
comment_width = 100
wrap_comments = true
normalize_comments = true

(see .rustfmt.toml)

Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>

rust/pvsecret/src/cmd/create.rs

@@ -213,7 +213,7 @@ fn write_secret(secret: &AddSecretType, asrcb: &AddSecretRequest) -> Result<()>
             .map(|c| if c.is_whitespace() { '_' } else { c })
             .collect();
 
-        //write non confidential data (=name+id) to a yaml
+        // write non confidential data (=name+id) to a yaml
         let secret_info = serde_yaml::to_string(asrcb.guest_secret())?;
         if stdout.to_owned() {
             println!("{secret_info}");