Treat log's key-values as attributes in log bridge #4799

Job	Run time
test (stable)	6m 21s
lint	3m 36s
external-types (opentelemetry)	59s
test (beta)	6m 37s
non-default-examples (opentelemetry-otlp/examples/basic-otlp)	39s
cargo-deny	24s
external-types (opentelemetry-sdk)	1m 11s
coverage	3m 9s
external-types (opentelemetry-otlp)	1m 14s
docs	1m 26s
external-types (opentelemetry-zipkin)	1m 13s
msrv	3m 14s
	30m 3s

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