Fix problems with the userAgent implementation

[capricorn86]

There are a bunch of problems with the user agent that we need to resolve.

1. Be able to detect Happy DOM as a user agent
Add "HappyDOM/v{version}" to the default user agent, where {version} is the current version package.json.

2. Make it possible to pass user agent as an option
Make it possible to pass "userAgent" as an option to the Window constructor.

3. Resolve issues with React console warnings
This is related to facebook/react#24283

We want to disable the "Download the React DevTools" log for a better development experience" log entries somehow in Jest and Vitest.

We should consider changing the user agent to be more similar to JSDOM ("Mozilla/5.0 (linux) AppleWebKit/537.36 (KHTML, like Gecko).

Another option is to default to a different user agent in Vitest and Jest.