Improve sub-items buttons

Improve sub-items table buttons style:

[1] Edit button. Change button for an Icon Edit button. See link included for related story where it's described (EZP-28360);

[2] Priority buttons:

• Add to .c-table-view_body .c-table-view-item_cell--priority:

  cursor: pointer;
  

  And for styling within the row, the suggested changes:

  .c-table-view-item__inner-wrapper c-table-view-item__inner-wrapper--input {
  padding: 2px 0;
  margin-top: -3px;
  }
  .c-table-view-item__priority-actions {
  margin-top: 4px;
  }
  

• Change background colors:
• .c-table-view-item__btn--submit
  Background-color: $ez-color-secondary;
  Hover state background-color: darken($ez-color_secondary, 15%);
• c-table-view-item__btn--cancel
  Background-color: $ez-color-base-medium;
  Hover state background-color: darken($ez-color-basemedium, 15%);

[3] Update upload button.
Remove text and keep only upload icon.
For reference on styling, see linked story included regarding styling button within table headers (EZP-28036)