Add new GREL function to support Jsoup parent() function to complement our select()

[thadguidry]

There is no easy way to navigate up the parse tree provided by jsoup selector syntax. We currently can navigate down very easily with Jsoup's selector syntax value.parseHtml().select("div > p") and also value.parseHtml().select("div:has(@) ~ div") but
this does not directly allow DOM traversal itself. However, Jsoup conveniently provides DOM traversal for finding a https://jsoup.org/apidocs/org/jsoup/nodes/Element.html#parent()
which mimics the behavior from BeautifulSoup's https://www.crummy.com/software/BeautifulSoup/bs4/doc/#parent

Proposed solution

Add a new GREL function for the jsoup method parent() and for simplicity sake just call the GREL function parent()

Alternatives considered

A difficult path of custom installed Jython 2.7 with BeautifulSoup

Additional context

Existing code for select() functionality is here:
https://github.com/OpenRefine/OpenRefine/blob/master/main/src/com/google/refine/expr/functions/xml/SelectXml.java
and function registration to be added to is here:
https://github.com/OpenRefine/OpenRefine/blob/master/main/src/com/google/refine/grel/ControlFunctionRegistry.java#L249