Remove mapping types

[dreamer-89]

As part of v2.0 release, mapping types are getting removed from OpenSearch engine. Below are the changes in the opensearch-engine.

• Removal of type from rest end-points
• Removal of include_type_name parameter from API requests.

As part of this issue, please verify if type removal change on OpenSearch engine impacts this repository. If yes, then please remove the type references/usage from this plugin.

Top level changes are captured in gist below:
https://gist.github.com/dreamer-89/d76eaf639171e8ab32fa7f8b9d6c93d3

For more detailed changes, please check meta issue below:
Related: OpenSearch-engine meta issue

[cliu123]

Mapping type is not being used in security-dashboards-plugin.