[Discover] Adjust log.level indicator alignment (elastic#195098)

##  📓 Summary

A change in the EuiDataGrid style clashed with a custom CSS change
applied to the grid in order to render the `log.level` indicator on the
whole line height.

This change fixes the spacing issue and delegates to the inner element,
the indicator itself, the responsibility to make fill the whole space
ignoring padding imposed by the grid (using an absolute positioning, the
DOM node will ignore inner spacing and fill the parent container.)



https://github.com/user-attachments/assets/fe8d418a-5c7f-4999-86a4-296304d5aa97

Co-authored-by: Marco Antonio Ghiani <marcoantonio.ghiani@elastic.co>

packages/kbn-unified-data-table/src/components/custom_control_columns/color_indicator/color_indicator_control_column.tsx

@@ -42,6 +42,8 @@ const ColorIndicatorCell: React.FC<ColorIndicatorCellParams> = ({ getRowIndicato
       data-test-subj="unifiedDataTableRowColorIndicatorCell"
       title={label}
       css={css`
+        position: absolute;
+        top: 0;
         background: ${color};
         width: ${COLOR_INDICATOR_WIDTH}px;
         height: 100%;

packages/kbn-unified-data-table/src/components/data_table.scss

@@ -83,7 +83,6 @@
   }
   .euiDataGridRowCell.euiDataGridRowCell--controlColumn[data-gridcell-column-id='colorIndicator'] .euiDataGridRowCell__content {
     height: 100%;
-    padding: 0;
     border-bottom: 0;
   }