Update population projection and growfactors for TAXYEAR=2022

[martinholmer]

Fixes issue #446. This pull request does the following things:

• renames puf_growfactors.csv as taxdata25_growfactors.csv
• renames cbo_population_projection.yaml as cbo25_population_projection.yaml
• adds cbo26_population_projection.yaml
• adds taxdata26_growfactors.csv from taxdata PR 456
• confirms generated TMD files are unchanged when TAXYEAR=2021
• recalibrates imputation parameters for TAXYEAR=2022

[donboyd5]

@martinholmer, this seems like a nice, clean way to preserve history and set up a framework for new growfactors when we have them. The minor adjustments to expected values for tests seem minimal.

Not surprisingly, make clean && make data passed for TAXYEAR 2022 and 2021.

I think the source note is slightly confusing and possibly not as accurate is it should be. It says,

# CBO Jan 2026 publication "The Demographic Outlook: 2026 to 2056"
# URL: https://www.cbo.gov/publication/61879
# (a) Data Underlying Figures, Figure 2 spreadsheet tab,
#     Total Population (millions) [for years from 2022 through 2056]
# (b) Demographic Projections, Population and growth spreadsheet tab,
#     Total Social Security area population (millions) [for years after 2056]

Every year I checked against the spreadsheet data source from CBO (tab "1. Population and growth", file "61879-Demographic-Projections.xlsx", in zip https://www.cbo.gov/system/files/2026-01/57059-2026-01-Demographic-Projections.zip) matches to all 3 decimal digits, all the way out to 2075. CBO gives, as the source note for the data, "Data source: Congressional Budget Office." So maybe it's better to just give a cite for "The Demographic Outlook: 2026 to 2056, January 2026" as the source.

When I asked Claude for an APA citation I got (after correcting a minor mistake that Claude also had because it could not access the web version):

Congressional Budget Office. (2026, January). The demographic outlook: 2026 to 2056. https://www.cbo.gov/publication/61879

I'd probably make first letter of demographic and outlook capitalized.

As far as I'm concerned, merging is good.

[martinholmer]

@donboyd5, Thanks for the advice on the CBO population data citation. I changed the comment to clarify that no one CBO spreadsheet has the population for all the years needed in the YAML file.