Fix Acknowledge Alert Request class loader issue

[eirsep]

Change transport ack alerts action to accept Action Request and recreate as AckAlertRequest to fix Acknowledge Alert Request class loader issue

Solving the same issue we faced earlier with notifications for ack alerts flow : opensearch-project/common-utils#37

Signed-off-by: Surya Sashank Nistala snistala@amazon.com

[eirsep]

Failure is from

org.opensearch.alerting.resthandler.FindingsRestApiIT > test find Finding by monitor id FAILED
    ParsingException[Failed to parse object: expecting token of type [START_OBJECT] but found [END_OBJECT]]
        at __randomizedtesting.SeedInfo.seed([CC40F800EF50801E:30D603E49DDE66AF]:0)
        at app//org.opensearch.common.xcontent.XContentParserUtils.parsingException(XContentParserUtils.java:[97](https://github.com/opensearch-project/alerting/actions/runs/3292387973/jobs/5427689051#step:4:98))
        at app//org.opensearch.common.xcontent.XContentParserUtils.ensureExpectedToken(XContentParserUtils.java:90)
        at app//org.opensearch.commons.alerting.model.FindingWithDocs$Companion.parse(FindingWithDocs.kt:59)
        at app//org.opensearch.alerting.AlertingRestTestCase.searchFindings(AlertingRestTestCase.kt:709)
        at app//org.opensearch.alerting.resthandler.FindingsRestApiIT.test fin

which is not related to this PR

this failure arises from common utils PR: fix security-analytics alerting findings api integration