fix(spy): fix spyOn types with optional method

[hi-ogawa]

Description

• Closes spyOn unable to infer type when using Partial TypeScript utility type #7674

It looks like opitonal key is intended to work, but Required wrapper is missing in a few cases. Jest does it a bit differently by moving Required<T> to generic side, but the idea seems same https://github.com/jestjs/jest/blob/4e7d916ec6a16de5548273c17b5d2c5761b0aebb/packages/jest-mock/src/index.ts#L1112.

On second thought, this doesn't necessary make things more type-safe. Waiting for a better use case from OP in #7674 (comment).

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time. If the feature is substantial or introduces breaking changes without a discussion, PR might be closed.
• Ideally, include a test that fails without this PR but passes with it.
• Please, don't make changes to pnpm-lock.yaml unless you introduce a new test example.

Tests

• Run the tests with pnpm test:ci.

Documentation

• If you introduce new functionality, document it. You can run documentation with pnpm run docs command.

Changesets

• Changes in changelog are generated from PR name. Please, make sure that it explains your changes in an understandable manner. Please, prefix changeset messages with feat:, fix:, perf:, docs:, or chore:.

[netlify]

✅ Deploy Preview for vitest-dev ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	8dad836
🔍 Latest deploy log	https://app.netlify.com/sites/vitest-dev/deploys/67d677063069090008e65c9e
😎 Deploy Preview	https://deploy-preview-7679--vitest-dev.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.