Start implementing a filter data type that could allow us to incrementally improve our code by moving one array at a time to the filter object

[ekluzek]

Description of changes

Implementing a filter object type as described here:

#829 (comment)

And in this design document:

https://docs.google.com/document/d/1RGPZZKSC9L5P9Q0mTIVFSTq9Lxf5mxnNJE72p4Je0r4

Specific notes

Contributors other than yourself, if any:

• @billsacks
• @samsrabin

CTSM issues resolved or otherwise addressed, if any:

• Resolves Allow arrays to only span certain landunits and/or related ideas that replace filters #829

Any user interface changes (namelist or namelist defaults changes)?

No

Testing planned or performed, if any:

• unit testing passing so far

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. Briefly describe tested configuration(s):
• 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:
• 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?: a