Update FATES testdefs so that we use the compset instead of a testmod directory

[adrifoster]

Description of changes

Rearranged and edited some of the FATES testdefs files so that we just use the compset for FATES SP mode.

Specific notes

• Created a new FATES testdef folder FatesColdDefBasic that just has a shell_commands file in it with necessary commands: ./xmlchange CLM_FORCE_COLDSTART="on" and ./xmlchange BFBFLAG="TRUE"

• Removed reference to fates_sp user mod as this is covered by SP compset for FatesColdDefReducedComplexSatPhen, FatesColdDefMeganReducedComplexSatPhen, and FatesColdDefDryDepReducedComplexSatPhen

• Updated one of the FATES SP tests to use just the FatesColdDefBasic user mods (thus only utilizing the FATES SP compset)

Contributors other than yourself, if any: @ekluzek

CTSM Issues Fixed (include github issue #):
Fixes #1817

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

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

Testing performed, if any:

Ran individual test cases for all changed tests. Running actual test suite next. Will report back results.

[adrifoster]

As per discussion with @ekluzek I am going to revert back some of these changes to keep references to the FatesColdDef in most of the modified testdefs, but update one of the test lists (the FATES SP one) to use the new FatesColdDefBasic user mod.