Add log exception support to Logger API/SDK

[iblancasa]

Is your feature request related to a problem? Please describe.

The Logs API/SDK in opentelemetry-python does not currently support emitting exceptions via the Logger API. This is now part of the spec.

The API introduces “Exception (optional)” parameter on emit() and the SDK requirement to map exceptions to exception.* attributes.

Describe the solution you'd like

Implement exception support for logs in opentelemetry-python.

Additional context

• Spec issue to stabilize logs exceptions: Stabilize the (optional) Exception parameter to Logger Emit opentelemetry-specification#4858
• OTEP: https://github.com/open-telemetry/opentelemetry-specification/blob/main/oteps/4430-span-event-api-deprecation-plan.md
• Logs API spec: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/api.md#emit-a-logrecord
• Logs SDK spec: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/sdk.md

I will send a PR regarding this.