keep stdout logs when tracing-flame/jaeger is enabled

Previously, enabling the `tracing_flame` or `allow_jaeger` options would
prevent any logs from being written to stdout. In addition, enabling the
`allow_jaeger` option would inhibit the `tracing_flame` option.

Now that we have a way to use separate tracing filters with different
layers, we can enable all three at the same time without issues.

This commit also prevents the `debug log_level` command from modifying
the `tracing-flame` filter. This was supported previously, but I don't
think it's something that you would ever want to do intentionally. Now
that we have both the normal log filter and the `tracing-flame` filter
enabled at the same time, we want to `debug log_level` to only modify the
normal filter.