[SCHEMA] Add datatypes field to datatype rule files

[tsalo]

Closes None.

Changes proposed:

• Add a datatypes field to the datatype rule files, so that the folder structure in the rules folder can be for readability, rather than something that implies the schema's structure.

What we won't tackle in this PR, but which is important, is that the schema code needs to be updated to use the new datatypes field instead of the directory/filename structure that is currently used to organize the schema.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.50%. Comparing base (ee9e8b5) to head (e2bafcc).

Additional details and impacted files

@@                Coverage Diff                @@
##           schema-sprint    #1012      +/-   ##
=================================================
+ Coverage          70.53%   71.50%   +0.96%     
=================================================
  Files                  9        9              
  Lines                930      930              
=================================================
+ Hits                 656      665       +9     
+ Misses               274      265       -9     

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[effigies]

Plan on merging this with or without schemacode changes to make the field available to tooling. Note that merging as is will mean that we can't take advantage of the reorganization potential until there are schemacode changes.