windows: have a machine run tests in an elevated env

[refack]

Refs: nodejs/node#23691
Refs: nodejs/node#23596

[joaocgreis]

Windows machines already run tests in an elevated environment, exactly because of this.

What happened with test-require-symlink was that the link was actually created and some programs like Node and Git Bash were actually able to use it. However, on Windows Explorer it appears as a useless .symlink file, suggested it was never meant to be used that way.

What probably broke the test was some recent Windows update. Node stopped being able to read the link, and the test started failing. We didn't see this in CI because we use Windows 10 Long Term Support Channel. I will see if we can use a different Windows 10 edition in CI to get more frequent updates.

[joaocgreis]

The test was fixed by nodejs/node#23691 and the general case by nodejs/node#23724.