Derive SIRS kernel coefficients for NIRSpec and NIRISS

[stscijgbot-jp]

Issue JP-3832 was created on JIRA by David Law:

JP-3622 recently implemented SIRS reference pixel subtraction as an option for NIRCam, noticeably reducing 1/f noise in a generic manner for all observations that include reference pixels.  This ticket is to derive the necessary coefficients for the NIRSpec and NIRISS detectors as well, which may be able to similarly benefit from this technique.