Add capability to imgest and assimilate IASI-NG

[wx20jjung]

• Is this a breaking change (a change in existing functionality)? NO

• Does this change require a documentation update? NO

• Does this change require an update to any of the following submodules? YES

  • [X ] GSI Added to GSI develop 11/25

How has this been tested?

I have run cycled tests with these changes using IASI-NG proxy data on Hera.
I have also conducted limited unit tests with my changes within the global-workflow:
C96C48_hybatmDA
C96_atm3DVar
Both pass when the OBSPROC namelist variable is removed or the latest develop branch of the GSI is used.

Checklist

• Any dependent changes have been merged and published
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have documented my code, including function, input, and output descriptions
• My changes generate no new warnings
• New and existing tests pass with my changes
• This change is covered by an existing CI test or a new one has been added
• Any new scripts have been added to the .github/CODEOWNERS file with owners
• I have made corresponding changes to the system documentation if necessary