Allow omitting LogRecord in favor of build pattern in Logging SDKs (open-telemetry/oteps#183)

The discussion while implementing the Java SDK revealed that the LogRecord
data type may not be necessary. See here open-telemetry/opentelemetry-java#3759 (comment)

However, in some other languages LogRecord fits nicely (see the comment about
Python implementation in the same comment thread).

This changes allows implementators of the OTEP to choose the most idiomatic
approach for their language.

Author: tigrannajaryan

oteps/logs/0150-logging-library-sdk.md

@@ -79,6 +79,12 @@ Methods:
   trace context related fields (TraceId,SpanId,TraceFlags) if applicable before
   making the call. Open Question: do we need to also pass the Baggage so that
   log processors and exporters can use it if they see the need?
+
+  Note: some languages may opt to avoid having a LogRecord data type and instead
+  use a more idiomatic builder pattern to prepare and emit a log record (see
+  e.g.
+  [Java discussion](https://github.com/open-telemetry/opentelemetry-java/pull/3759#discussion_r738019425))
+
 - Flush.
 
 ### LogRecord