Replace deprecated rules

[fabulousgk]

These rules are deprecated and should be removed from the configs...

no-buffer-constructor
no-return-await
no-empty-interface

[fregante]

They need to be replaced with:

• https://github.com/eslint-community/eslint-plugin-n/blob/master/docs/rules/prefer-global/buffer.md
• https://typescript-eslint.io/rules/no-empty-object-type

no-return-await has been inexplicably dropped just because "it's not a perf improvement" anymore 🤷‍♂️ https://eslint.org/docs/latest/rules/no-return-await
Thankfully TS still has its own no-return-await. I think it can stay here until eslint actually drops the rule in v10