WPS region picker

[na9da]

What this PR does

Port region picker input for WPS from terriajs v7.

The WPS input parameter is described as below by setting a special mime type:

<Input minOccurs="1" maxOccurs="1">
   <ows:Identifier>region</ows:Identifier>
   <ows:Title>Region to run analysis</ows:Title>
   <ows:Abstract></ows:Abstract>
   <ComplexData maximumMegabytes="10">
     <Default>
       <Format>
         <MimeType>application/vnd.terriajs.region+json</MimeType>
       </Format>
     </Default>
   </ComplexData>
</Input>

The Execute request will have the parameter filled as below:

<wps:Input>
  <ows:Identifier>region</ows:Identifier>
  <wps:Data>
    <wps:ComplexData>{"regionType":"SA2","region":"51203"}</wps:ComplexData>
  </wps:Data>
</wps:Input>

Note the JSON payload with keys regionType and region. The region corresponds to the value of regionProp property specified in the region map definition. For SA2 it corresponds to sa2_5dig11. Should we change this to property name instead?

This currently requiresWMS type region mapping servers (or region maps with analyticsWmsServer configured).
See example region mapping definition.

Test me

Steps:

1. Load this CI link with custom config.json > parameters > regionMappingDefinitonsUrl.
2. Open the WPS catalog item from the catalog explorer
3. You should see a parameter with Select region button - click it to start the region selection flow.

UI screenshot:

Checklist

• There are unit tests to verify my changes are correct or unit tests aren't applicable (if so, write quick reason why unit tests don't exist)
• I've updated relevant documentation in doc/.
• I've updated CHANGES.md with what I changed.
• I've provided instructions in the PR description on how to test this PR.