[Vue] when getting plugin path relative to webroot, try all possible webroots #19362

Description:

As title.

Review

• [ ] Functional review done
• [ ] Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• [ ] Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• [ ] Security review done
• [ ] Wording review done
• [ ] Code review done
• [ ] Tests were added if useful/possible
• [ ] Reviewed for breaking changes
• [ ] Developer changelog updated if needed
• [ ] Documentation added if needed
• [ ] Existing documentation updated if needed

latest version shown to work on matomo for wordpress

@diosmosis would you mind rebasing this one onto next_release. We still haven't released the final 4.11. So might be good to include that one, so it can make it into matomo for wordpress soon.

@sgiehl done