Convert old array and string helpers into their modern class-based methods.

Before

camel_case('Foo Bar');
ends_with('Foo Bar', 'Bar');
starts_with('Foo Bar', 'Foo');
str_contains($string, 'Bar');
str_plural($string, $count);
array_except($array, ['key']);
array_get($array, 'key');

After

Str::camel('Foo Bar');
Str::endsWith('Foo Bar', 'Bar');
Str::startsWith('Foo Bar', 'Foo');
Str::contains($string, 'Bar');
Str::plural($string, $count);
Arr::except($array, ['key']);
Arr::get($array, 'key');