qpainter canvas: get rendering intent

So we can use that when converting the projection to display.
The interesting this is that we thought blackpoint wasn't used
either, but it is, in KoLcmsColorConversionTransformation::createTransform:

    KConfigGroup cfg = KGlobal::config()->group("");
    bool bpCompensation = cfg.readEntry("useBlackPointCompensation", false);

    int flags = 0;

    if (bpCompensation) {
        flags = cmsFLAGS_BLACKPOINTCOMPENSATION;
    }
    cmsHTRANSFORM tf = cmsCreateTransform(srcProfile->lcmsProfile(),
                                          srcColorSpaceType,
                                          dstProfile->lcmsProfile(),
                                          dstColorSpaceType,
                                          renderingIntent,
                                          flags);

I'm not sure how much performance reading this config entry every time
we create a transform takes, though.

CCBUG:301235