Test for p:insert 021 (AB)

The pipeline

<p:declare-step xmlns:err="http://www.w3.org/ns/xproc-error" xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
   <p:output port="result"/>
   <p:insert match="/doc/processing-instruction()" position="first-child">
      <p:with-input>
         <doc><?pi text?></doc>
      </p:with-input>
      <p:with-input port="insertion">
         <doc2/>
      </p:with-input>
   </p:insert>
   <p:wrap-sequence wrapper="wrap"/>
</p:declare-step>