Improve inference for tuple types

[graphemecluster]

See this thread in your Twitter community.

But I think you shouldn't merge until microsoft/TypeScript#48663 is being solved or it will affect development experience, so I made this PR a draft.

[graphemecluster]

I don't think TypeScript is going to solve microsoft/TypeScript#44309 in a short time due to compatibility issues. So maybe you can promote this library there afterwards w

[graphemecluster]

Another approach that doesn't require microsoft/TypeScript#48663 to be solved is to replace all the occurrences of ...args: ValueIndexPair<this, T> by the ordinary way value: T, index: Indices<this>, array: this.

[graphemecluster]

Unfortunately I don't know why the test failed (it also failed in my computer); the two types should be identical. And I didn't touch lib.es2017.object.d.ts either. Am I missing something…?

[graphemecluster]

Lastly I would like to know the reason to repeat the utility types in both lib.es5.d.ts and lib.util.d.ts.

[graphemecluster]

Regarding the test, I doubt T[] isn't the same as T[] | []. I will just keep the error here for the time being.

[graphemecluster]

Close due to excessive changes.