make swathBounds available

[oarcher]

swathBounds are available in annotation (xpath '/product/swathMerging'). ( ref Sentinel-1 Product Specification from IPF 2.9x to 3.3x , p 182)

We should be able to decode it as a geodataframe.

_NoiseLut has also a '.block' property that should be compared to those swath bounds

xsar/src/xsar/sentinel1_xml_mappings.py

Lines 371 to 375 in 40340e2

	# to geopandas
	blocks = pd.concat(blocks, axis=1).T
	blocks = gpd.GeoDataFrame(blocks)
	return _NoiseLut(blocks)

[vincelhx]

@agrouaze i added swathBounds in a datatree, but didn't make this comparison.
as a reminder