mksurfdata_esmf: Refactor mksoiltex

[samsrabin]

Description of changes

Refactors mksoiltex() subroutine to make it easier to understand and avoid duplicated code.

Specific notes

Contributors other than yourself, if any: None

CTSM Issues Fixed (include github issue #): None

Are answers expected to change (and if so in what way)? No

Any User Interface Changes (namelist or namelist defaults changes)? No

Does this create a need to change or add documentation? Did you do so? No

Testing performed, if any:

• Builds without error
• Runs without error
• Outputs are bit-for-bit identical with previous version (organic_o option 1)
• Outputs are bit-for-bit identical with previous version (disabled organic_o option 2) Removing that code

Other remaining tasks

• Rename is_neg_4 to be more meaningful. I think it indicates sand dunes, but is that really true for ALL variables or just PCT_SAND?
• Can block at TODO: Remove as unnecessary? be removed?
• Remove organic_o option 2

[samsrabin]

Output surface dataset at 1.9x2.5 resolution as of 9a2759f is bit-for-bit identical with version from ctsm5.2.027. However, my implementation of organic_o option 2—which is hard-coded off, as before—produces differences when forced on. I wonder if it would make sense at this point to just remove that code?

[slevis-lmwg]

@samsrabin I think it's ok to remove "option 2" at this point. There's record of it if we ever decide to resuscitate it.

Also, is this PR affected by the latest updates that occurred here?

[samsrabin]

Thankfully no, this touches a different part of the code.