Added audit event graphql type

What does this MR do and why?

Added audit event graphql type which is accessed from project compliance violation type.

How to set up and validate locally

1. You need to have a group with Ultimate license.
2. Required data, you can do either of following steps:
   1. You can checkout branch hraghuvanshi-comp-violations-seeder and run command FILTER=compliance_report_data SEED_COMPLIANCE_REPORT_DATA=1 GROUPID=<group_id> bundle exec rake db:seed_fu for filling required data and you can run query.
   2. Create all items manually:

      1. You need to have at least one project under the group, atleast one audit event related to the project.

      2. Also, have at least one compliance framework in the group, the framework should have atleast one compliance control.

      3. The framework should be applied to the project.

      4. Now create a compliance violation entry in the database by running following command in the rails console:

         ComplianceManagement::Projects::ComplianceViolation.create(project_id: <project_id>, namespace_id: <namespace_id>, audit_event_id: <audit_event_id>, compliance_requirements_control_id: <compliance_requirements_control_id>, status: 0, audit_event_table_name: 0)

3. Now run the following query by using the above compliance violation id in the graphql explorer, you should get all the details of the violation:

query projectComplianceViolation {
  projectComplianceViolation(
    id: "gid://gitlab/ComplianceManagement::Projects::ComplianceViolation/<id>"
  ) {
    id
    status
    complianceControl {
      id
      name
    }
    project {
      id
      name
      fullPath
      webUrl
    }
    auditEvent {
      id
      eventName
      targetId
      targetDetails
      targetType
      details
      ipAddress
      entityPath
      entityId
      entityType
      author {
        id
        name
      }
      project {
        id
        name
      }
      group {
        id
        name
      }
      user {
        id
        name
      }
    }
  }
}

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Related to #542342 (closed)