[9.x] Add cache-based maintenance mode support

[axlon]

Thanks to PR #40070 by @wimulkeman Laravel's maintenance mode is now configurable, this PR builds on this idea further by adding cache-based maintenance mode. This is especially useful when a Laravel application is distributed over multiple servers behind a load balancer, or for serverless Laravel applications. This solution uses Laravel's cache system and is not limited to a single cache solution.

Config would look something like the following:

// config/app.php

'maintenance' => [
    'driver' => 'cache',
    'store' => 'my-cache-store', // Optional, default store is used if none is passed here
],