Description of proposed changes

• spatial_filter.py: Fix the np.pad() pad_width integral type error while using the double_difference filter, as described in double_difference yields TypeError: pad_width must be of integral type. #1014.

• writefile.write(): do not overwrite format for .hgt file, as it can be float64 in isce2. Plus, the two-band format in roipac is weird anyway and not used much anymore [in the last 3+ years if I remember correctly].

• isce_utils.extract_alosStack_metadata(): make los_file optional, because 1) attribute CENTER_INCIDENCE_ANGLE is not essential, i.e. optional; and 2) los_file does not exist sometimes, as in the post-processing of alos2App

Reminders

• Fix double_difference yields TypeError: pad_width must be of integral type. #1014
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