acknowledge api unresponsive when plugins.alerting.filter_by_backend_roles is enabled

[sbcd90]

Issue #, if available:

Description of changes:
Acknowledge Alerts transport action internally makes a call to Get monitor transport action to get the corresponding monitor object belonging to the alert. https://github.com/opensearch-project/alerting/blob/main/alerting/src/main/kotlin/org/opensearch/alerting/transport/TransportAcknowledgeAlertAction.kt#L88

the Get monitor transport action first validates the backend roles before proceeding. https://github.com/opensearch-project/alerting/blob/main/alerting/src/main/kotlin/org/opensearch/alerting/transport/TransportGetMonitorAction.kt#L87
But Acknowledge Alerts transport action already stashes the threadcontext before making Get monitor transport action call. https://github.com/opensearch-project/alerting/blob/main/alerting/src/main/kotlin/org/opensearch/alerting/transport/TransportAcknowledgeAlertAction.kt#L86
So, the user received from threadcontext by Get monitor transport action is null. https://github.com/opensearch-project/alerting/blob/main/alerting/src/main/kotlin/org/opensearch/alerting/transport/TransportGetMonitorAction.kt#L81

hence it throws following exception:

AlertingException[Filter by user backend roles is enabled with security disabled.]; nested: Exception[org.opensearch.OpenSearchStatusException: Filter by user backend roles is enabled with security disabled.];
    at org.opensearch.alerting.util.AlertingException$Companion.wrap(AlertingException.kt:70)
    at org.opensearch.alerting.transport.SecureTransportAction$DefaultImpls.validateUserBackendRoles(SecureTransportAction.kt:82)
    at org.opensearch.alerting.transport.TransportGetMonitorAction.validateUserBackendRoles(TransportGetMonitorAction.kt:50)
    at org.opensearch.alerting.transport.TransportGetMonitorAction.doExecute(TransportGetMonitorAction.kt:79)
    at org.opensearch.alerting.transport.TransportGetMonitorAction.doExecute(TransportGetMonitorAction.kt:50)
    at org.opensearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:219)
    at org.opensearch.indexmanagement.controlcenter.notification.filter.IndexOperationActionFilter.apply(IndexOperationActionFilter.kt:39)
    at org.opensearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:217)
    at org.opensearch.indexmanagement.rollup.actionfilter.FieldCapsFilter.apply(FieldCapsFilter.kt:118)
    at org.opensearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:217)
    at org.opensearch.performanceanalyzer.action.PerformanceAnalyzerActionFilter.apply(PerformanceAnalyzerActionFilter.java:78)
    at org.opensearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:217)
    at org.opensearch.security.filter.SecurityFilter.apply0(SecurityFilter.java:320)
    at org.opensearch.security.filter.SecurityFilter.apply(SecurityFilter.java:165)
    at org.opensearch.action.support.TransportAction$RequestFilterChain.proceed(TransportAction.java:217)
    at org.opensearch.action.support.TransportAction.execute(TransportAction.java:189)
    at org.opensearch.action.support.TransportAction.execute(TransportAction.java:108)
    at org.opensearch.client.node.NodeClient.executeLocally(NodeClient.java:110)
    at org.opensearch.client.node.NodeClient.doExecute(NodeClient.java:97)
    at org.opensearch.client.support.AbstractClient.execute(AbstractClient.java:476)
    at org.opensearch.alerting.transport.TransportAcknowledgeAlertAction$doExecute$1$1$getMonitorResponse$1.invoke(TransportAcknowledgeAlertAction.kt:99)

& call becomes unresponsive.

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[praveensameneni]

Can you please backport to all the supported versions after the PR is reviewed and merged

[engechas]

CI failing, code LGTM

[riysaxen-amzn]

CI is failing

[goyamegh]

Please check the failing CIs.