Eslint config cleanup (#1424)
* Replace deprecated ESLint rules
See: https://eslint.org/docs/rules/#deprecated
* ESLint: switch `0`, `1` and `2` to `off`, `warn` and `error`.
* Simplify no-async rule
* Cleanup disable comments
* Switch ESLint config to YAML
See: https://eslint.org/docs/user-guide/configuring#configuration-file-formats
