migration_dependencies.optional ignored since 6.1.3

Problem/Motivation

Since migrate_tools 6.1.3, migrations are no longer executed in the correct dependency order.
Specifically, the `migration_dependencies.optional` key is ignored, and `migrate:status` does not display migrations in the order they will actually run.
This is a side effect of the change introduced in #2969227, which aimed to improve performance by filtering migrations before instantiation.

Steps to reproduce

1. Define a migration with `migration_dependencies.optional` pointing to another migration.
2. Run `drush migrate:status` or `drush migrate:import `.
3. Observe that the optional dependency is not executed before the dependent migration.
4. Compare with the same setup on migrate_tools 6.1.2 – the order and optional dependency are respected.

Proposed resolution

Restore dependency-based ordering for filtered migrations in `migrationsList()`.
The patch should:
- Use the already-instantiated migrations (after requirements checks)
- Call `buildDependencyMigration()` on this filtered set
- Ensure `required` and `optional` dependencies are respected
- Avoid re-instantiating all migrations to maintain performance.

User interface changes

None. The `migrate:status` output will now correctly reflect dependency order.

API changes

None. Only internal ordering of migrations is affected.

Data model changes

None. The underlying migration definitions and dependencies remain unchanged.