[Actionable Observability] Add to new and existing cases bulk actions in Alerts page

Relates to https://github.com/elastic/kibana/issues/131122

📝 Summary

This PR adds bulk actions for cases in the timelines and security plugins. Currently in o11y Alerts page checkboxes and bulk actions are completely hidden.

Acceptance criteria

Enable checkboxes in Alerts table by removing showCheckboxes prop
Disable status bulk actions. Enabling checkboxes in Step 1 above will make Mark as Acknowledged and Mark as Closed options enabled by default. This PR introduces a new flag to turn status bulk actions off. Pass this prop to the tGrid table

bulkActions: {
        alertStatusActions: false,
}

Pass a new customBulkActions prop that was introduced as part of this PR

bulkActions: {
        alertStatusActions: false,
        customBulkActions: [
          {
            label: ADD_TO_NEW_CASE,
            key: 'attach-new-case',
            'data-test-subj': 'attach-new-case',
            disableOnQuery: true,
            disabledLabel: ADD_TO_CASE_DISABLED,
            onClick: (items?) => {
              const caseAttachments = [];
              createCaseFlyout.open({ attachments: caseAttachments });
            },
          },
          {
            label: ADD_TO_EXISTING_CASE, 
            key: 'attach-existing-case',
            disableOnQuery: true,
            disabledLabel: ADD_TO_CASE_DISABLED,
            'data-test-subj': 'attach-existing-case',
            onClick: (items?) => {
              const caseAttachments = [];
              selectCaseModal.open({ attachments: caseAttachments });
            },
          },
        ],
       }
}

Suggestion

As a next step we could make add to new case and add to existing case bulk actions appear by default in the timelines plugin since both consumers, security_solution and observability, want to show these bulk actions by default. We could add a new flag to switch them off similar to how status bulk actions are built:

bulkActions: {
        caseActions: false,
}

This is the code that needs be moved inside the timelines plugin if we want to follow this approach. The introduction of customBulkActions could be used in case a consumer wants to add extra bulk actions.

elastic / kibana