[10.x] Add Macroable trait to Sleep class

[bradietilley]

From #47092

This PR adds the Macroable trait to the Sleep class. Example:

// AppServiceProvider
Sleep::macro('forConfiguredTime', static function () {
    $milliseconds = DB::table('settings')->where('key', 'sleep_after_action')->first()->value ?? 1000; // let's say 3500 ms

    return Sleep::for($milliseconds)->milliseconds();
} );

// Throughout your application:
Sleep::forConfiguredTime(); // e.g. 3500ms

// Or
Sleep::for(1)->second()->orMyCustomMacroAmountOfTime();

A helpful subfeature for this facility would be the ability to define a replacement duration. Example:

$sleep = Sleep::for(1)->second();

// Replace the duration
$sleep->duration(800)->milliseconds();

// $sleep = 800ms not 1s

[nunomaduro]

Ups! You will need to adjust your testItCanReplacePreviouslyDefinedDurations test - one idea is create a macro to override the duration

[nunomaduro]

I've fixed the test suite.