Audit event streaming update: moving delete and verification token to the list itself

Problem

With the Update on the issue, we are moving Edit away from the eclipse dropdown. We should move others as well.

Before	After

Implementation steps

• Remove the disclosure dropdown and related code from stream_item.vue
• Remove the verification token modal from stream_item.vue
• Move deletion logic to stream_destination_editor.vue and emit event 'delete' event from stream_destination_editor.vue to stream_item.vue
• Add danger "Delete destination" button to the right bottom of stream_destination_editor.vue -> only show if destination is being edited, not when being created
• Add GlFormInputGroup with a clipboard copy button and the verification token (with label) to stream_destination_editor.vue
• Update specs accordingly
• Update documentation

Verification steps

• Go to issue-reproduce audit events – streams tab
• Verify that destination does not have an ellipsis button on the right (previously with options Edit, View verification token, and Delete)
• Expand the destination by clicking on the url
• Verify there is an input "Verification token" with the token value and clicking the copy clipboard icon actually puts the token value in your clipboard
• Verify there is a "Delete destination" button on the bottom right of the destination. Select it and verify it open the delete confirmation modal
• Create a new destination by selecting "Add streaming destination"
• Verify it does not have an input with the Verification token, nor a "Delete destination" button