feat(querymodifier): add opt-in query parameter sorting and generated tests

[duffn]

Summary

Add opt-in query-parameter ordering without changing existing filtering behavior:

includeparams(url, names)          -> retain matching parameters in input order (unchanged)
includeparams_sorted(url, names)   -> retain matching parameters, then sort by raw name
sortparams(url)                    -> sort all parameters by raw name

Sorting is stable: repeated names retain their value order. Names are compared as raw, case-sensitive strings; nothing is URL-decoded. Callers should opt in only when their origin treats reordered parameters the same way. This does not change a consumer's VCL automatically.

Add VTC coverage for cache-key sharing and duplicate-name order, plus a seeded differential harness that checks the built VMOD against an independent query-string model. Refresh the Docker build to use the Docker Hub Varnish 8.0.2 Alpine image and run both suites.

Evidence

• Before: distinct-name parameter order yielded separate URLs/cache keys; there was no opt-in sorting function or generated comparison harness.
• After: Varnish 8.0.2 Docker build passed 16/16 VTC tests and 211 generated cases (seed 2026). Local Varnish 9.1 passed the same VTC suite and generated runs with seeds 2026 and 17.
• Not checked: older Varnish versions or origin-specific equivalence for every consumer. GitHub Checks should be consulted for remote gates.

Merge Danger

Door: Two-way. Existing entry points keep their behavior; callers must explicitly use the new functions. Reverting the VMOD change is straightforward before consumers adopt it.

Blast Radius: VMOD consumers opting into sorted URLs. Reordering can change meaning for origins that interpret distinct query parameters in order; repeated raw-name values remain stable, but URL-encoded aliases are not decoded or unified.