Window transformer with `window_shift=None` should have coordinate axis for new axis

[cboulay]

ezmsg-sigproc/src/ezmsg/sigproc/window.py

Lines 179 to 185 in c433d64

	self._state.out_newaxis = replace(
	axis_info,
	gain=0.0
	if self.settings.window_shift is None
	else axis_info.gain * self._state.window_shift_samples,
	offset=0.0, # offset modified per-msg below
	)

Currently, when using window_shift=None, we are setting the gain of the new axis to 0.0. This was my old shorthand for 'irregular axis'. Now we have a CoordinateAxis class so we should use that instead.

Barely anyone using the Window node in an ezmsg graph will have encountered this because we usually yield windows one-by-one anyway, effectively dropping the new axis.