Remove query_builder from mypy typing issues list

[cursor]

Summary

• remove sentry.snuba.metrics.query_builder from the mypy "sentry modules with typing issues" override list
• fix all mypy errors in src/sentry/snuba/metrics/query_builder.py by tightening type narrowing, introducing a typed helper for metric operation params, and handling optional branches safely
• keep runtime behavior unchanged while making the module pass strict type checking

Testing

• PATH="/workspace/.venv/bin:$PATH" mypy --config pyproject.toml src/sentry/snuba/metrics/query_builder.py
• PATH="/workspace/.venv/bin:$PATH" .venv/bin/python -m tools.mypy_helpers.mypy_without_ignores src/sentry/snuba/metrics/query_builder.py
• PATH="/workspace/.venv/bin:$PATH" .venv/bin/python tools/mypy_helpers/check_stronglist.py pyproject.toml
• PATH="/workspace/.venv/bin:$PATH" .venv/bin/prek run -q

Notes

• Focused pytest runs were attempted, but this environment has no running Redis (localhost:6379 connection refused), so Django/pytest suites could not complete here.

@armenzg please review.

Legal Boilerplate

Look, I get it. The entity doing business as "Sentry" was incorporated in the State of Delaware in 2015 as Functional Software, Inc. and is gonna need some rights from me in order to utilize my contributions in this here PR. So here's the deal: I retain all rights, title and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Sentry can use, modify, copy, and redistribute my contributions, under Sentry's choice of terms.