fix(query-core): make retry failureCount 1-based

[KyungHwanKim-devs]

🎯 Changes

• Fix retry callback failureCount to start at 1 on the first failure (query-core)
• Add a regression test covering retry callback counts
• Document the 1-based failureCount in retry docs

Fixes TanStack#10017

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested this code locally with pnpm run test:pr. (Ran npx nx run @tanstack/query-core:test:lib)

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).