Tests are disabled and out of date in response_parser_test.go

[fridgepoet]

What happened:
response_parser_test.go_ has an underscore at the end of the file name. https://github.com/grafana/opensearch-datasource/blob/main/pkg/opensearch/response_parser_test.go_

Not sure if this was intentional; it's been there since the first commit of this repo.

The consequence is that no test in that file is run under go test.

• Rename it without the _ at the end.
• All of the tests need to be verified and assertions need to be updated.

[fridgepoet]

This is what the test was copied from originally, can probably use it to update some of the tests:
https://github.com/grafana/grafana/blob/main/pkg/tsdb/elasticsearch/response_parser_test.go

[fridgepoet]

Closing this now but a few more tests need to be re-enabled #175