Update SPI ingestion to 2022-23

[MaxGhenis]

Summary

• switch SPI private prerequisite downloads from spi_2020_21.zip to the existing spi_2022_23.zip private HF artifact
• centralize the current SPI release name, tab filename, fiscal year, and H5 filename in datasets/spi.py
• update income imputation to train from put2223uk.tab
• scope the cached income QRF model by SPI release metadata so old 2020-21-trained income.pkl files are not silently reused
• make SPI age and region handling tolerate current-file codes like AGERANGE=-1 and GORCODE values outside 1-12 without silently mapping them to London
• regenerate storage/incomes_projection.csv from the 2022-23 SPI input and make the projection builder validate/rebuild stale SPI H5 files before use
• keep full income model training at 100k SPI draws, while reducing the TESTING=1 data-build sample to 10k so PR CI stays bounded

Context

policyengine/policyengine-uk-data-private already contains spi_2022_23.zip and spi_2022_23.h5, but the income-imputation donor path still pointed at spi_2020_21/put2021uk.tab. I did not find an open issue specifically for that donor-file switch.

Related open issues are about target vintages rather than this private prerequisite path:

• Refresh HMRC SPI targets to tax year 2023-24 #388 refreshes HMRC SPI targets to 2023-24
• Regenerate SPI income projection targets from the 2023-24 base #393 regenerates SPI income projection targets from a 2023-24 base

This PR advances the current SPI microdata input to 2022-23 and regenerates the checked-in SPI income projections from that base. The remaining stale non-SPI private inputs are tracked separately in #411.

Validation

• TESTING=1 uv run --python 3.13 pytest policyengine_uk_data/tests/test_income_projection.py policyengine_uk_data/tests/test_spi_build.py policyengine_uk_data/tests/test_frs_prerequisites.py -q
• uv run --python 3.13 ruff format --check policyengine_uk_data/datasets/imputations/income.py policyengine_uk_data/utils/incomes_projection.py policyengine_uk_data/tests/test_spi_build.py
• git diff --check