Add logs

[pdudits]

Like @donbourne noted, this API is not really intended for end users. Rather the runtimes should assure that their application and system logs are exported over appropriate OpenTelemetry channel.

For that we would need:

• support configuration of log exporters otel.logs.exporter
• document service loading capability of LogRecordExporter

Then the reasonable requirement would be that application's logs capture reasonable context information and other telemetry attributes -- the feature that could actually be implemented on top of LogRecordBuilder. But there's no standard we can build upon here as each vendor uses different logging API and there's no common one that would be supported in applications e. g. by means of injection.

[Emily-Jiang]

Is JUL the one every runtime supports?

[Emily-Jiang]

I believe I have addressed all of your comments @donbourne @pdudits @brunobat . Please re-review and approve or add more comments. Thanks

[Emily-Jiang]

@brunobat @pdudits please review again to see whether you have any further comments. I would like to merge this on Monday next week. thanks