`metadata: :all` in >= 7.0.0 includes `file` as a charlist

[zachdaniel]

Seeing this kind of snippet in our JSON logs after upgrading:

"metadata":{"line":365,"file":[....]}

Having the line and file included by default is all good TBH, but having the file formatted as a charlist probably isn't what folks would be expecting when including the file.

EDIT: for context, line and file don't appear to have been included in metadata: :all in < 7.0.0

[smaximov]

This also happens if you explicitly specify :file in the metadata config:

LoggerJSON.Formatters.Basic.new(metadata: [:file])

I've opened a PR with the fix: #159

[cigrainger]

Caught this with otel_trace_flags as well!