[9.x] Fixes memory leak on anonymous migrations

[nunomaduro]

This pull request resolves an issue with memory leaks in Laravel test suites that utilize anonymous migrations. The leak is a result of an internal memory issue within PHP when anonymous classes are utilized. It is important to note that this fix will only be noticeable if the user uses the RefreshDatabase trait, and in-memory databases.

// Use case 1: 702 feature tests

// Before:
Time: 00:23.628, Memory: 324.00 MB
// After
Time: 00:21.393, Memory: 40.00 MB

---
// Use case 2: 233 feature tests

// Before:
Time: 01:03.643, Memory: 147.00 MB
// After
Time: 01:01.898, Memory: 82.50 MB

Fixes #46029.