feat(types): add better promise support in expects and matchers

[samchungy]

Description

Resolves #6279

At the moment, when you use .resolves or .rejects the type generics get lost due to the Promisify function.

import { expect } from "vitest";

interface FooBar {
  foo: string;
}

expect({ foo: "bar" }).resolves.toStrictEqual<FooBar>({ foo: "bar" });
expect({ foo: "bar" }).toStrictEqual<FooBar>({ foo: "bar" });

See error

This PR changes the types and allows us to also type-check the resolves and reject matchers as well as properly types custom matchers as promises.

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[samchungy]

This previously wasn't returning a Promise.

[samchungy]

Technically breaking but this aligns more with how Jest works and makes more sense?

See: https://github.com/vitest-dev/vitest/pull/8266/files#diff-810c1bb9ffac48cfe14f7dbbaf10fdf5725e06feecb99c657d49f3c7712bcd00L197-R197

I think we may be incorrectly setting these as it seems like the intention is for void to be R and T to be set to E here.

[samchungy]

Tests seem flakey and out of control of my PR

[sheremet-va]

expect(val).resolves.eq(val) no longer returns a Promise

[samchungy]

Added a test and fixed that! Thanks for catching! There's so many cases 🥲

[sheremet-va]

We decided that with the amount of breaking changes in Vitest 4 already, we need to postpone this at least to Vitest 5 because the impact is quite big, but it fixes a niche use case

[samchungy]

Fair enough! feel free to tag me when it's time to revisit