Reduce again the number of match calls (#7815)

- Reduce the number of match calls (see commit messages)
- A few miscellaneous improvements

crates/nu-test-support/src/playground/director.rs

@@ -99,17 +99,14 @@ impl Executable for Director {
                     }
                 }
 
-                let process = match binary
+                let process = binary
                     .construct()
                     .stdout(Stdio::piped())
                     // .stdin(Stdio::piped())
                     .stderr(Stdio::piped())
                     .arg(format!("-c '{}'", commands))
                     .spawn()
-                {
-                    Ok(child) => child,
-                    Err(why) => panic!("Can't run test {}", why),
-                };
+                    .expect("It should be possible to run tests");
 
                 process
                     .wait_with_output()

crates/nu-test-support/src/playground/matchers.rs

@@ -48,10 +48,8 @@ impl CheckerMatchers for Play {
             Some(out) => out,
             None => return Ok(()),
         };
-        let actual = match str::from_utf8(actual) {
-            Err(..) => return Err(format!("{} was not utf8 encoded", description)),
-            Ok(actual) => actual,
-        };
+        let actual =
+            str::from_utf8(actual).map_err(|_| format!("{} was not utf8 encoded", description))?;
 
         if actual != *out {
             return Err(format!(