On Linux and macOS, no program output was being observed.
This is referenced in the [LocalTime] docs for `tracing-subscriber`,
which links to this [unsoundness issue] in the time crate.
Rather than introducing a possible vector for undefined behaviour and
segfaults, I have just changed the logging to use UTC time instead.
When running the ASB as a systemd service, one would generally use the
`--disable-timestamps` flag anyway as systemd adds its own timestamps
which can be local to the server.
If the situation with `tracing-subscriber` and the time crate is fixed
then this can be updated.
This commit also updates the `tracing-subscriber` and `tracing-appender`
dependencies, closing #987.
[LocalTime]: https://docs.rs/tracing-subscriber/latest/tracing_subscriber/fmt/time/struct.LocalTime.html
[unsoundness issue]: https://github.com/time-rs/time/issues/293#issuecomment-748151025
Previously logs were only timestamped when the ASB was run in an
interactive terminal or if the logs were output as JSON. JSON logs and
ASB output in an interactive terminal are no longer timestamped by
default.
