Add --match-tests to 'check' cmd

[KtorZ]

For running only tests matching a certain pattern. Useful when doing TDD.

For example:

aiken check --match-tests list

[rvcas]

this could be an if let

if let Some(search_str) = match_tests {
    if !path.to_string().contains(&search_str) {
        continue;
    }
}

or even

if matches!(match_tests, Some(search_str) if !path.to_string().contains(search_str) ) {
    continue;
}

[KtorZ]

Cool stuff. Thanks :)