Add an ability to override default BatchingSettings in LoggingServiceV2StubSettings

[losalex]

Recently we implemented the ability to edit batching settings in java-logging library due to customers demand - see 1164.
Thats said, LoggingServiceV2StubSettings is still lacking functionality to expose BatchingSettings to users. So far it seems not used much, however this issue will keep track for cases when users will demand such ability.