suggest `assertArrayHasKey` after `assertTrue(isset($x))`

```diff
-$this->assertTrue(isset($anything["foo"]), "message");
+$this->assertArrayHasKey("foo", $anything, "message");
```

similar to `AssertSameNullExpectedRule` and others

could be auto-fixable.

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[inspired by rector](https://getrector.com/blog/make-phpunit-tests-perfect-in-15-diffs)