OGR VRT should not propagate ignoring of x and y cols of a PointFromColumns to the source layer

[Even Rouault]

With test.csv :

x,y
2,49

and

test.vrt:

<OGRVRTDataSource>
    <OGRVRTLayer name="test">
        <SrcDataSource relativeToVRT="0">tmp/test.csv</SrcDataSource>
        <SrcLayer>test</SrcLayer>
        <GeometryField encoding="PointFromColumns" x="x" y="y"/>
        <Field name="x" type="Real"/>
        <Field name="y" type="Real"/>
    </OGRVRTLayer>
</OGRVRTDataSource>

calling SetIgnoredFields(['x', 'y']) on the VRT layer prevents the geometry from being built.

This is not expected as the external user of a VRT layer should not have knowledge that x and y are used to build the geometry

[Even Rouault]

trunk r28158, branches/1.11 r28159 "OGR VRT: do not propagate ignoring of x and y cols of a PointFromColumns to the source layer (#5777)"