[Vue] patch vue compiler so it does not decode   entities #18770

Description:

As title. I thought of skipping the UMD files, but I'm not sure why the test was originally added, and it looked related to security. Since   could be easily needed in the future it also doesn't seem acceptable to just never use it.

I found the place where this happens in the vue compiler and found a way to patch it.

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

@diosmosis it still failed https://app.travis-ci.com/github/matomo-org/matomo/jobs/559193206. I guess just replace<p>&nbsp;</p> to <br/> maybe

@peterhashair that will fix it now, but it means using   in vue templates is not allowed which seems like it could become a problem.

I can find one simple way to fix this but it the result still requires remembering and explaining something, so I don't think its much better than having to explain that   cannot be used directly in templates. Will close this.