[8.x] Add File::lines($path) method

[JosephSilber]

Many of the most useful scenarios for using lazy collections involves reading files line by line (see here for more details).

This PR adds a lines method to the Filesystem class, to lazily read the lines of a file:

$collection = File::lines($path);

Example

With this in place, you can easily read Laravel's logs lazily (using the new chunkWhile method):

$pattern = '/^[\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d]/'; // starts with e.g. [2020-09-07 00:24:11]

$logs = File::lines(storage_path('logs/laravel.log'))
    ->chunkWhile(fn ($line) => ! preg_match($pattern, $line));

The $logs variable will now be a lazy collection, from which we can pull out a single log entry at a time.

[GrahamCampbell]

Lazy collections could be quite appropriate for paginating eloquent queries tbh. Currently there's an each method, but we could "go native" as it were, and have a way to do getLazy() or something.