[11.x] Skip the number of connections transacting while testing to run callbacks

[tonysm]

Changed

• Skip the number of connections transacting on tests to run callbacks correctly

---

The testing DatabaseTransactionsManager was hardcoding the number of
connections to skip as 1. In a multi-db context, it must skip the same
number of connections transacting defined on the tests.

related PRs: #48523
resolves #53334

[tonysm]

@crynobone could you take a look at the changes here as well, pls? The mentioned discussion has some examples:

<?php

namespace Tests\Feature;

use Illuminate\Foundation\Testing\RefreshDatabase;
use Illuminate\Support\Facades\DB;
use Tests\TestCase;

class ExampleTest extends TestCase
{
    protected array $connectionsToTransact = ['sqlite', 'second'];

    use RefreshDatabase;

    public function test_with_nested_transaction_on_default_connection(): void
    {
        $executed = false;

        // Works as expected...
        DB::transaction(function () use (&$executed) {
            DB::afterCommit(function () use (&$executed) {
                $executed = true;
            });
        });

        $this->assertTrue($executed); // SUCCEEDS!
    }

    public function test_without_nested_transaction_on_default_connection(): void
    {
        $executed = false;

        // Should execute right away, since there are no application-level 
        // transactions (only the two from the tests), but it doesn't...
        DB::afterCommit(function () use (&$executed) {
            $executed = true;
        });
        
        $this->assertTrue($executed); // FAILS!
    }
}

[crynobone]

@tonysm I added EloquentTransactionWithAfterCommitUsingRefreshDatabaseOnMultipleConnectionsTest

Wondering if there any good tests we can add to cover using multiple database connection.

[tonysm]

@crynobone I've added some tests, can't think of any other useful examples