Do not call pure Misc methods through registry

[jtojnar]

These have a singular purpose and except for parse_uri do not interact with other classes. Overriding them makes little sense.

This makes the code a bit cleaner and less opaque for static analysis.

I am ignoring Misc::error since it will go away and Misc::xml_encoding because it accesses registry.

Partly reverts f6e63e6

[Art4]

As much as I like this PR, but this would be a breaking change. Instead we could create non-static methods in Misc class and calling them with $registry->create(Misc::class)->.... Then we can deprecate the $registry->call() method.

[jtojnar]

@Art4 I do not see what does this change break.

Or do you mean that it changes the behaviour that the methods will no longer be overridable? I do not see how that could be considered breaking any promises any more than any other implementation change would.

[Art4]

Something like this will not work anymore:

<?php

class CustomMisc extends \SimplePie\Misc
{
    public static function fix_protocol($url, $http = 1)
    {
        // custom implementation ...
        return $url;
    }
}

$simplepie = new \SimplePie\SimplePie();
$simplepie->get_registry()->register('Misc', CustomMisc::class);

$simplepie->set_feed_url('url_where_the_protocol_should_be_fixed_with_my_implementation');