Add 4.x output support for legacy labor_supply_response macro result

[anth-volk]

Context

policyengine-api-v2 needs a 4.x-supported way to produce the legacy single-year macro labor_supply_response section. Pre-1 Simulation.calculate_economy_comparison() returned this in the public macro output. In policyengine 4.x, country packages still contain labor-supply-response variables/parameters, but I did not find a first-class output helper that reconstructs the legacy response object.

This blocks the simulation API from migrating back to 4.x without changing the public SingleYearMacroOutput contract used by API/report callers.

Proposed work

Add a 4.x output helper that computes the legacy labor_supply_response result, including the aggregate fields and decile/hour breakdowns expected by existing callers.

Acceptance criteria

• Provide a .py output helper for labor_supply_response or a documented replacement.
• Match the pre-1 output shape and sign conventions used by calculate_economy_comparison().
• Cover US and UK behavior, including cases where response parameters are disabled or zero.
• Add tests for aggregate totals, decile breakdowns, and hours fields.