Add support for batching configuration #903
Description
Expose an ability to customize batching settings introduced in 1164.
Also batching settings should be available through standard logging adapters like slf4j/logback, for example:
<appender name="CLOUD" class="com.google.cloud.logging.logback.LoggingAppender"> <writeSynchronicity>ASYNC</writeSynchronicity> <autoPopulateMetadata>true</autoPopulateMetadata> <batchingSettings> <flowControlSettings> <maxOutstandingElementCount>100000</maxOutstandingElementCount> <limitExceededBehavior>Ignore</limitExceededBehavior> </flowControlSettings> </batchingSettings> </appender>