Enhancement: Add more issues found to the Troubleshooting page [Innovation Day]

[andrasguseo]

🎫 Ticket

[Innovation Day]

🗒️ Description

On the Events/Tickets > Troubleshooting page there is a section displaying issues found on the website.
There are limited to 4 issues.
This PR adds another 3 issues that are common and can help prevent the customers opening support tickets.
The added issues are:

• PHP version check: flags if the PHP version is less than 8.0
• The default PHP time zone is NOT set to UTC, as this can cause issues with event times
• A caching plugin is detected

Note, there's no changelog entry yet.

🎥 Artifacts

Screenshot of the Troubleshooting page showing the 3 new issues:
https://www.dropbox.com/scl/fi/5zkjoef4qg3fs0tt8pozy/shot_240719_205012.jpg?rlkey=zpx9c1j2ugdg5hghmlckspwp6&e=1&dl=0

✔️ Checklist

• Changelog entry in the readme.txt file.
• Code is covered by NEW wpunit or integration tests.
• Code is covered by EXISTING wpunit or integration tests.
• Are all the required tests passing?
• Automated code review comments are addressed.
• Have you added Artifacts?
• Check the base branch for your PR.
• Add your PR to the project board for the release.

[bordoni]

Address the code style issues pointed out by PHPCS.