Add rule to detect completely useless object spread

[ajafff]

Since microsoft/TypeScript#26798 there are no longer excess property errors for object spread. That also means you can spread anything, even if it doesn't have any property in common with the contextual type.

declare let foo: {a: string, b: string};

let bar: {c: string} = {...foo, c: ''}; // spreading `...foo` doesn't contribute any useful properties to `bar`
let foobar: {a: string, c: string} = {...foo, c: ''}; // this is valid because there is at least one overlapping property
let baz = {...foo, c: ''}; // this is valid because there is no contextual type
let bas: Record<string, string> = {...foo, c: ''}; // this is valid because of the index signature

I have no strong opinion whether this should be a new rule or integrated into an existing rule.
For a reference implementation regarding object spread, see no-duplicate-spread-property