Unify validation suite metadata around tests/v1

[Mahaprasadnanda]

Summary

• add compatibility support to the validation suite schema
• teach bin/jsonschema_suite to filter and rewrite tests/v1 for a concrete dialect
• annotate the unified tests/v1 cases with compatibility metadata
• document the new runner expectations for the unified suite
• fix the suite checker to read JSON files as UTF-8 on Windows

Verification

• python bin/jsonschema_suite check
• python bin/jsonschema_suite flatten --dialect draft7 tests/v1/pattern.json
• python bin/jsonschema_suite flatten --dialect draft2020-12 tests/v1/optional/format-annotation.json

Notes

• this keeps the legacy per-draft directories in place for now while making tests/v1 consumable by runners
• the compatibility metadata was inferred in bulk from the existing per-draft files, with targeted overrides for renamed or unified-only cases

[karenetheridge]

Could you please link to the issue that this relates to?

[Mahaprasadnanda]

@karenetheridge It was a qualification task for [https://github.com/json-schema-org/community/issues/994#issuecomment-3961376424]

[jdesrosiers]

This is not the qualification task. Read the issue carefully and ask question in slack if you can't figure it out.