Rename RequestBatchBuffer methods from 'flushable' to 'extract' to clarify it doesn't do the flushing#6485

joviegas merged 4 commits intomasteraws/aws-sdk-java-v2:masterfrom

joviegas/refactor_RequestBuffer_namesaws/aws-sdk-java-v2:joviegas/refactor_RequestBuffer_namesCopy head branch name to clipboard