polygonize: add _validate_raster on raster input

[brendancol]

Description

polygonize() currently checks only raster.ndim != 2. Non-DataArray and non-numeric-dtype inputs raise confusing errors:

• polygonize(np.zeros((10, 10))) -> AttributeError on .data etc.
• polygonize(xr.DataArray(complex_arr)) -> fails inside numba.

xrspatial/polygonize.py:1623.

Expected behavior

polygonize calls _validate_raster(raster, ...) to surface a clean TypeError / ValueError at the API boundary.

Proposed fix

Replace the raster.ndim != 2 check with _validate_raster(raster, func_name='polygonize', name='raster', ndim=2). Keep the additional shape[0] >= 1 and shape[1] >= 1 guard since _validate_raster does not enforce that.