Add 529 plan contribution deduction to New Mexico state income tax

[MaxGhenis]

Summary

New Mexico offers a state income tax deduction for contributions to 529 education savings plans. This is not currently implemented in PolicyEngine.

What needs to happen

1. Add NM 529 contribution deduction parameters (caps by filing status)
2. Create a variable for the NM 529 subtraction
3. Integrate into NM AGI subtractions

The existing person-level variable investment_in_529_plan can be used as the input.

Note: New Mexico allows an unlimited deduction for 529 contributions.

Context

Flagged during a meeting with Matt Comey (JCT) and Dan Feenberg (NBER/TAXSIM) as a gap in state tax calculators.