Deem SSI resources from parents to children

The SSI resource test logic only considers the individual's resources, or marital unit's if married: https://github.com/PolicyEngine/policyengine-us/blob/master/policyengine_us/variables/gov/ssa/ssi/eligibility/resources/meets_ssi_resource_test.py

SSI rules deem resources from parents to children similarly to how it does so for income: https://www.ssa.gov/ssi/text-resources-ussi.htm

Start with policyengine_us/variables/gov/ssa/ssi/eligibility/resources/meets_ssi_resource_test.py and compare its current individual and marital-unit logic with the project's existing SSI income deeming rules. Consult the linked SSA resource guidance, then verify that parent resources are accounted for when evaluating children and that the resource test reflects the documented SSI rules.

Written by the indexing model from the issue text.