[5.8] Add set/get accessors for MigrationCreator stubPath

[hastinbe]

Very straight-forward, makes the stub path mutable so we can use our own stubs. This is beneficial for those who want different schemas than the defaults with the migration commands. For one example, I want increments() over bigIncrements() (#26472) without having to change it with each migration

Example usage from a service provider:

$this->app->extend('migration.creator', function ($creator, $app) {
    return tap($creator)->setStubPath(__DIR__.'/../../database/migrations/stubs');
});

[taylorotwell]

I think I would rather have a more comprehensive solution to overriding stubs.

[hastinbe]

I agree that would be nice, but if you search this you'll see people have been wanting to change the stub path since Laravel 4.2. They are stuck with solutions like overriding MigrationCreator and replacing laravel's in the service container, using composer scripts to overwrite the stubs in the vendor directory, and custom artisan commands. Just to change the stub path. I hope you reconsider that this is just a small change that fulfills a simple need until a more comprehensive solution becomes available. Thanks