fix bug in gdal -> mintpy corner coordinate convention

[sssangha]

Description of proposed changes

Through the ARIA products workflow, or whenever loading a gdal file in general, an erroneous shift appears to be applied to the accessed geotransform and the derived x_first and y_first fields. Specifically, an extra half pixel shift (to the north and west) is applied when the gdal geotransform object already reports the coordinates of the upper left pixel.

I've tracked this bug in a few scripts, but would like advise on where else I should look to track down potential persistent issues.

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[yunjunz]

Thank you @sssangha for the careful checking! I introduced this bug in prep_aria in #542. As you said, gdal (and aria, hyp3, and gmtsar by extension) use the upper-left corner of the upper-left pixel as the first coordinates, which is the same as roipac and mintpy, thus, no extra half-pixel shift is needed. I believe you captured all the occurrences in the code. Feel free to squash and merge the PR whenever you are ready please.