[10.x] Allow separate directory for locks on filestore

[Gaitholabi]

Issue:

When using the file driver, upon executing php artisan cache:clear or calling \Cache::flush();, all locks are cleared.

Similar to what other drivers offer, this PR adds the ability to define a separate directory for Locks when using the file driver.

Example:

        'file' => [
            'driver' => 'file',
            'path'   => storage_path().'/framework/cache',
            'lock_path' => storage_path().'/framework/lock',
        ],

• Backward compatible, not adding the lock_path config would yield the same result as before
• Makes the FileStore driver more consistent with other drivers namely RedisStore and Database store