EZP-31474 - fix embed anchor link converting to richtext

[ITernovtsii]

Question	Answer
JIRA issue	EZP-31474
Type	Bug
Target version	1.9
BC breaks	no
Doc needed	no

Currently, the converter works incorrectly for this XML:

<?xml version="1.0" encoding="utf-8"?>
<section xmlns:image="http://ez.no/namespaces/ezpublish3/image/" xmlns:xhtml="http://ez.no/namespaces/ezpublish3/xhtml/" xmlns:custom="http://ez.no/namespaces/ezpublish3/custom/">
  <paragraph xmlns:tmp="http://ez.no/namespaces/ezpublish3/temporary/">
    <link anchor_name="maincontent">
      <embed size="original" align="top" node_id="241190"/>
    </link>
  </paragraph>
</section>

It will result to empty object inserted into embed

<ezembed xlink:href="ezlocation://241190" ezxhtml:class="ez-embed-type-image">
	<ezlink/>
	<ezconfig><ezvalue key="size">original</ezvalue>ezconfig>
</ezembed>

This PR fixing it, so <ezlink xlink:href="#maincontent"/> will be created in converter.

TODO:

• Implement feature / fix a bug.
• Implement tests + specs and passing ($ composer test)
• Fix new code according to Coding Standards ($ composer fix-cs).
• Ask for Code Review.

[vidarl]

Thank you. Would you be able to create a test for this? for instance in https://github.com/ezsystems/ezplatform-xmltext-fieldtype/tree/1.9/tests/lib/FieldType/Converter/Xslt/_fixtures

[ITernovtsii]

@vidarl Done. Added fixtures for the use-case.