Add support for php 8.2

[tenzap]

Output of tests with php 8.2 is as follows:

1) Install_test::test_index
ErrorException: Creation of dynamic property Install_test::$request is deprecated

Test declaration:

class Install_test extends TestCase
{
//...
	public function test_index()
	{
		$output = $this->request('GET', 'install');
	}
//...
}

[kenjis]

CI3 does not support PHP 8.2. See #409