Interactive account passwords (#1623)

## Issue Addressed

#1437

## Proposed Changes

- Make the `--wallet-password` flag optional and creates an interactive prompt if not provided.
- Make the `--wallet-name` flag optional and creates an interactive prompt if not provided.
- Add a minimum password requirement of a 12 character length.
- Update the `--stdin-passwords` flag to `--stdin-inputs` because we have non-password user inputs 

## Additional Info

lighthouse/tests/account_manager.rs

@@ -408,7 +408,7 @@ fn validator_import_launchpad() {
     File::create(src_dir.path().join(NOT_KEYSTORE_NAME)).unwrap();
 
     let mut child = validator_import_cmd()
-        .arg(format!("--{}", import::STDIN_PASSWORD_FLAG)) // Using tty does not work well with tests.
+        .arg(format!("--{}", STDIN_INPUTS_FLAG)) // Using tty does not work well with tests.
         .arg(format!("--{}", import::DIR_FLAG))
         .arg(src_dir.path().as_os_str())
         .arg(format!("--{}", VALIDATOR_DIR_FLAG))