Re-enable ESLint rules `@typescript-eslint/prefer-*`

[MajorLift]

        '@typescript-eslint/prefer-enum-initializers': 'error',
        '@typescript-eslint/prefer-nullish-coalescing': 'warn',
        '@typescript-eslint/prefer-optional-chain': 'warn',
        '@typescript-eslint/prefer-reduce-type-parameter': 'warn',

In future PRs, enabling the 'prefer' rules should remove the need for some style guide entries (TODO: link entries)