Add create Pit api and fix sigv4 bug

[penghuo]

Description

• Add createPit api in OpenSearchClient.
• Upgrade Opensearch client to 2.11
• Fix SigV4 bug with Post request with empty body
• Add AWS Integregation test

sbt integtest/integration

[info] AWSOpenSearchAccessTestSuite:
[info] - should Create Pit on AWS OpenSearch
[info] Run completed in 3 seconds, 116 milliseconds.
[info] Total number of tests run: 1
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 1, failed 0, canceled 0, ignored 0, pending 0
[info] All tests passed.

Issues Resolved

#430

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.