Add geometryColumnName() method for WFS and OAPIF providers

[kannes]

Feature description

#59909 added https://qgis.org/pyqgis/master/core/QgsVectorDataProvider.html#qgis.core.QgsVectorDataProvider.geometryColumnName for some providers (ogr, hana, mssql, oracle, postgres, spatialite).

Would it be possible to extent this to the WFS and OAPIF providers too? (cc @nyalldawson)

For QGIS expression filters one can use $geometry. But when constructing SQL layer filters in Python that refer to the geometry, one needs to know the geometry column's name so this would greatly simply there.

Additional context

No response

[rouault]

for WFS, in #60191
for OAPIF, I don't think this makes sense currently. Nothing in the driver AFAICS and AFAIR knows about the geometry column name. This is somewhat implicit. Maybe some latest OGC API Features Part XXX have an explicit geometry column name, but it isn't yet there.