theoradec: Set telemetry options only if they are nonzero

Setting telemetry options, even to zero, causes libtheora to enable an expensive code path. For large enough videos (e.g. 1920x1080) this can increase the time to decode each frame by 30-40 ms, which can be enough to cause noticeable stutter.

I've tried to submit a patch upstream to libtheora for this issue, https://gitlab.xiph.org/xiph/theora/-/issues/2312. However, even assuming that patch is accepted, I expect it will be very slow to propagate to distributions.