Add module for designating patch/col/etc. as "debug"

[samsrabin]

Description of changes

Often we want to add write statements as part of debugging model behavior, but this can quickly become hard to parse if we don't limit the scope of the messaging. If we're debugging just one patch, column, gridcell, or landunit, we can make the messaging conditional on the object having the correct index. This PR adds a new module, debugMod, that facilitates this.

debugMod allows the user to hard-code a global index for patch, column, landunit, and/or gridcell to debug. It then provides functions where the user can give either a local or global index and get back a boolean that's true if it's the debugged one and false otherwise.

Specific notes

Contributors other than yourself, if any:

• None

CTSM issues resolved or otherwise addressed, if any:

• None

Any user interface changes (namelist or namelist defaults changes)? No

Testing planned or performed, if any:

• Tested during some column-level troubleshooting
• Add unit tests. Tricky because we don't want to hard-code any debug index.

Requirements before merge:

• I have followed the CTSM contribution guidelines.

• The code in this PR branch builds with no errors.
• The code in this PR branch runs with no errors. Column-level troubleshooting
• This either (a) does not change answers, (b) it only changes answers at roundoff level, or (c) I have performed a scientific evaluation of the answer changes. Which?: A

• I have reviewed relevant parts of the CLM documentation Tech Note or User's Guide to determine if anything needs to be changed or added. If it does, describe: Should add a bit in the Troubleshooting section of the User's Guide
• This PR either (a) does not create a need to update the documentation or (b) includes required documentation updates (see guidelines for contributing documentation). Which?: Will include updates, but I haven't made them yet.

[samsrabin]

Need to remove a bunch of unused things.

[samsrabin]

Need to uncomment all these.

[samsrabin]

Set this to -999.

[samsrabin]

Good idea from @mvdebolskiy: Add an option to the functions that would have them return true if any parent is debug. So for instance, you could set a column, landunit, or gridcell to debug, then do do_debug_patch(..., include_parent=.true.).