log: Add a possibility to convert standard attributes to log attributes

[pellared]

Add functions converting standard attributes to log attributes.

Originally posted by @pellared in open-telemetry/opentelemetry-specification#4201 (comment)

CC @bogdandrutu

[pellared]

It may become important if we decide that Logs (Bridge) API can be used directly to emit events.

[pellared]

It may become important if we decide that Logs (Bridge) API can be used directly to emit events.

It happened here: open-telemetry/opentelemetry-specification#4352