Integrated Alerting: Improvements to overall user experience for action buttons in Alerting

Following issues according to the design are to be fixed:

1. The size of the "Delete" button for all tabs should be bigger (attachment_1);
2. No explanation of the Action buttons if the user hovers over it (delete, duplicate, edit).
3. Explain the Threshold value on the list or while adding alert rules, what can be entered in the field (e.g. ><= not allowed) (attachment_3)
4. Add Severity colors for Alert Rules as for Alerts tab;
5. Fix scroll (attachment_4);
6. Explain and make bigger "Details" button (attachment_5);
7. Add table headers if no items found (Alerts tab and Alert Rules, Notification Channels) (attachment_6, attachment_7);
8. Add coloring to Rule Template uploading (attachment_8)