fix(coverage): prevent reportsDirectory from removing user's project

[AriPerkkio]

Description

Configuration below can remove user's whole project including local Git history from .git. One could accidentally use that when trying to generate coverage reports in the root of project instead of the default ./coverage, and find out that their whole project is now wiped (that's me 🙃).

// Don't run this
export default defineConfig({
  test: {
    coverage: {
      reportsDirectory: './',
    },
  },
})

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[hi-ogawa]

Maybe check also parent directory like ../?
Using root.startsWith(reportsDirectory) can cover root === reportsDirectory as a special case.

(Ah, I guess startsWith might not be it since "/some/directory".startsWith("/some/dir") is a false positive.)

[sheremet-va]

We can check startsWith(reportsDirectory + '/')

[AriPerkkio]

Sounds good. We can also add this improvement later on if you want to include this PR as is in the release @sheremet-va.