[19.0][IMP] base_view_inheritance_extension: wraptext

[hbrunn]

this finally lets us deal with text in upstream views that's not accessible to standard inheritance. When you have xml like

       <some>
           <node>
               plain text 1
               <other_node />
               plain text2
           </node>
       </some>

you're pretty much out of luck when you want to change either of the texts, you have to replace the whole node.

This PR allows to say

      <wraptext expr="//some/node" position="text" element="span" />
      <wraptext expr="//some/node/other_node" position="tail" element="div" />

in inherited views, which transforms the above to

       <some>
           <node>
               <span>plain text 1</span>
               <other_node />
               <div>plain text2</div>
           </node>
       </some>

that you can further modify with the inheritance machinery

[StefanRijnhart]

Nice one!

[NL66278]

👍 LGTM and tests are comprehensive.