Supersedes #3350
Clarifies the parameters for emitting a log record.
Context was particularly confusing. Context is not a property of the
`LogRecord` data model. Cleans up section of bridge API spec that seems
to suggest that Context is a field of `LogRecord`. Also, clarifies that
Context can be associated with an emitted LogRecord. We have similar
language in the trace API that leaves room for languages to achieve this
in an idiomatic way. See
d25734a47e/specification/trace/api.md?plain=1#L365-L370
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Co-authored-by: Reiley Yang <reyang@microsoft.com>