Add support for DomCrawler's PHPUnit assertions

[dunglas]

Allow to use all DomCrawler assertions introduced in Symfony 4.3 with Panther.

Example:

<?php

class AssertionsTest extends PantherTestCase
{
    public function testDomCrawlerAssertions(): void
    {
        self::createPantherClient()->request('GET', '/basic.html');
        $this->assertSelectorExists('.p-1');
        $this->assertSelectorNotExists('#notexist');
        $this->assertSelectorTextContains('body', 'P1');
        $this->assertSelectorTextSame('.p-1', 'P1');
        $this->assertSelectorTextNotContains('.p-1', 'not contained');
        $this->assertPageTitleSame('A basic page');
        $this->assertPageTitleContains('A basic');
        $this->assertInputValueNotSame('in', '');
        $this->assertInputValueSame('in', 'test');
    }
}

Requires symfony/symfony#32207.

[dunglas]

Needs symfony/symfony#33278