Fix error reporting in main and move all arg validation into fn args::parse (#585)

* Fix reporting parsing error from `args::parse`
   Report it in `args::parse` by using `Args::command().error(...).exit()`
   instead of returning `BinstallError`.
* Rm unused variant `BinstallError::OverrideOptionUsedWithMultiInstall`
* Refactor: Move `strategies` validation into `args::parse`
* Rm unused variant `BinstallError::InvalidStrategies`
* Add new unit test `args::test::verify_cli`

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

crates/bin/src/main.rs

@@ -18,10 +18,7 @@ fn main() -> MainExit {
     // This must be the very first thing to happen
     let jobserver_client = LazyJobserverClient::new();
 
-    let args = match args::parse() {
-        Ok(args) => args,
-        Err(err) => return MainExit::Error(err),
-    };
+    let args = args::parse();
 
     if args.version {
         println!("{}", env!("CARGO_PKG_VERSION"));