Chain our debug setting through to CSS Parser's leniency setting

[JakeQZ]

See MyIntervals/PHP-CSS-Parser#346.

We just need to pass on CssInliner::$debug through Pelago\Emogrifier\Css\CssDocument to Sabberworm\CSS\Parser, mostly with one line of code to be added:

$parserSettings = \Sabberworm\CSS\Settings::create()->withLenientParsing(!$debug);

This will resolve one of the failing tests in #1129.

But life is never simple. Simply applying the requried code change leads to a whole bunch of additional test failures, which need to be looked into. On initial glance, quite a few are because we expect an exception for malformed CSS but would now be getting a different class of exception. But there are other failures of a different nature too.