Include taxable IRA distributions in CBO target with taxable pensions and annuities

The CBO line is "Taxable pensions and annuities and IRA distributions" but we currently only tie it to `taxable_pension_income` (which includes annuities per our grouping in the CPS)

This won't immediately affect targeting but it will post #3079

Taxable IRA distributions are a quarter of total taxable pensions+annuities+IRAs, so this could be significantly reducing our accuracy.