[CodeQuality] Add AssertClassToThisAssertRector

[TomasVotruba]

Adds AssertClassToThisAssertRector to the code quality set.

Converts static PHPUnit\Framework\Assert::assert*() calls to $this->assert*() inside PHPUnit test classes.

The existing PreferPHPUnitThisCallRector only handles self::/static:: calls; fully-qualified Assert:: calls were not covered.

 use PHPUnit\Framework\Assert;
 use PHPUnit\Framework\TestCase;

 final class SomeTest extends TestCase
 {
     public function test()
     {
-        Assert::assertSame(1, 1);
+        $this->assertSame(1, 1);
     }
 }

Only rewrites when $this is usable — skips non-test classes, static methods, and static closures/arrow functions.