confusing parameter names for rf_cwd

### Brief summary of bug

Not sure if this is a feature or a bug? We've introduced a respiration fraction for coarse woody debris (CWD) to litter pools, but these are parameters on the parameter file are called two different things and read in differently. This potentially adds confusion in how the respiration fractions are used in CENTURY and MIMICS simulations.

specifically:
- `rf_cwdl2` is used by MIMICS and CENTURY (for CWD -> L2 pool); where as
- `bgc_rf_cwdl3` is only used by CENTURY for CWD -> L3 pool

Both values are set to 0.5 on the parameter set, but since they are named differently it's easy for users to get tripped up and only change one value.

### General bug information

**CTSM version you are using:** [output of `git describe`]
branch_tags/CMIP7_ciso.n01.alpha-ctsm5.4.CMIP7.11.ctsm5.3.075

**Does this bug cause significantly incorrect results in the model's science?** [Yes / No]
No

**Configurations affected:** [Fill this in if known.]
BGC

### Details of issue

The two parameters are read in differently here:
- https://github.com/ESCOMP/CTSM/blob/2c44dbeb6e00b1012d0f0fef3daa43848b4da15b/src/biogeochem/CNSharedParamsMod.F90#L107
- https://github.com/ESCOMP/CTSM/blob/2c44dbeb6e00b1012d0f0fef3daa43848b4da15b/src/soilbiogeochem/SoilBiogeochemDecompCascadeBGCMod.F90#L203

And used in:
- https://github.com/ESCOMP/CTSM/blob/2c44dbeb6e00b1012d0f0fef3daa43848b4da15b/src/soilbiogeochem/SoilBiogeochemDecompCascadeBGCMod.F90#L940
- https://github.com/ESCOMP/CTSM/blob/2c44dbeb6e00b1012d0f0fef3daa43848b4da15b/src/soilbiogeochem/SoilBiogeochemDecompCascadeMIMICSMod.F90#L1343