Update Jarvis detection logic

[wpalani]

Since now the .host-info file is moved to the host root we are updating the detection method.

We are also detecting using the file system instead of database check.

Proposed changes

Type of Change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• Linting and tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

[circlecube]

Looks good.

I do wonder if we should store it in a transient for a while rather than looking up the file on every page load. (Even if it's just an hour)