chore: Remove unused jsonschema dependency, declare attrs

[lukehsiao]

What this PR does / why we need it:

jsonschema's last consumer was the pre-0.10 repo_config.py, which used it to validate feature_store.yaml. That file was rewritten on pydantic for the 0.10 release in April 2021, so the dependency has been carried unused for roughly five years, surviving the setup.py to pyproject.toml consolidation along the way.

Dropping it exposed a real bug: feature_view_projection.py and openlineage/facets.py import attr directly, but attrs was never declared and only arrived transitively via jsonschema -> referencing -> attrs. A clean install without jsonschema fails at import feast. This patch declares attrs explicitly rather than migrating those files to stdlib dataclasses, which would change the runtime behavior of a core class and belongs in its own change.

The lock files were recompiled preserving existing pins instead of with make lock-python-dependencies-all, which re-resolves everything to latest and would bury this removal in unrelated churn. jsonschema stays in the minimal and ci locks because mcp requires it; the base locks drop jsonschema, jsonschema-specifications, referencing, and rpds-py. The ci locks also pick up scylla-driver, which the ci extra has required since the ScyllaDB online store landed but was never locked.

Tested: recompiled all 12 uv lock files with uv 0.9.25 targeting aarch64-apple-darwin (MACOSX_DEPLOYMENT_TARGET=15.0) to match the platform the checked-in locks were compiled on. The pybuild-deps build locks are untouched because the minimal-sdist package set is unchanged. In a fresh py3.12 venv, feast installs without jsonschema, import feast succeeds, and feast init followed by feast apply works end to end.

Checks

• I've made sure the tests are passing.
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Testing Strategy

• Unit tests
• Integration tests
• Manual tests
• Testing is not required for this change