[8.x] Added whenContains and whenContainsAll to Stringable

[telkins]

I mainly did this because I wanted to combine when() and contains(): whenContains(). I added whenContainsAll() since it was quite similar.

I would also have taken the time to implement whenXyz() for all of the "check-like" methods on the class:

• endsWith()
• exactly()
• is()
• isAscii()
• isUuid()
• test()
• startsWith()

Please let me know if it's worthwhile or not. I can definitely see it being valuable, so I'm happy to add these as well. 🤓

[telkins]

I realized that I ought to maybe make an example to demonstrate how this can help.

Unless I'm missing something, here's an example of how things might have to be done before this PR:

$stringable = Str::of('some important announcement');

if ($stringable->contains(['important', 'emergency'])) {
    $stringable->upper();
}

return (string) $stringable;

// SOME IMPORTANT ANNOUNCEMENT

After:

return (string) Str::of('some important announcement')
    ->whenContains(
        ['important', 'emergency'],
        fn (Stringable $stringable) => $stringable->upper(),
    );
}

// SOME IMPORTANT ANNOUNCEMENT