CCM-14750: Add multi-release release-check flow - #296

Description

This slice extends the release-check flow beyond a single release so we can validate the full ticket set represented by a broader release selection when needed.

It includes:

• support for comparing more than one release in a single run
• selector and aggregation logic for release ranges
• report updates needed to explain multi-release results clearly
• tests covering the expanded selection and comparison behaviour

Context

NHS releases do not often need side-by-side comparison across multiple release tags. The main use case for this slice is an initial production release, where we want to check all tickets that make up the build being released to prod for the first time.

This PR broadens the analysis surface so the release-check tooling can aggregate those commits and Jira versions into one governance check before any fix workflow is introduced.

Why this is a separate slice

Multi-release support builds directly on the proven single-release model, but it adds enough aggregation and reporting behaviour to deserve its own review. Keeping it separate makes it easier to validate the selector semantics and output changes in isolation.

Validation

• package install
• lint
• typecheck
• unit tests

Sensitive Information Declaration

• I confirm that neither PII/PID nor sensitive data are included in this PR and the codebase changes.