Write global/variable attributes defined in the yaml + subregional files update

[uramirez8707]

Description

• Adds code to write out the global/variable attributes defined in the yaml
• Writes out is_regional=.TRUE. as a global attribute if the file is subregional. This attribute is only going to exist if the file is subregional. FYI @ceblanton
• Updates tests to make sure this works

Fixes #1242

How Has This Been Tested?
CI

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included
• make distcheck passes