re-enable oversampling on PolarizedQProbe

[bmaranville]

refl1d.probe.PolarizedQProbe inherits from PolarizedNeutronProbe, but does not handle the inherited oversampling or oversampling_seed kwargs in the init, so deserialization is currently broken.

This PR adds these argument to the PolarizedQProbe.__init__, and calls the base class oversample(oversampling, oversampling_seed) method during initialization, properly oversampling all the xs.

This fixes the bug on deserialization, and also enables users of the class to take advantage of oversampling if it helps them in their fits.

[bmaranville]

This is a very targeted fix to an active bug affecting users, and is unlikely to have effects outside the scope of PolarizedQProbe, so merging without further review so it can be released.