[Bug][Investigations] - Limit sample size range input to integers (#185998)

## Summary

Currently you can enter a decimal value in the sample size range
selector which causes an error in the discover experience. This ticket
resolves that issue by limiting the actual parsed value to an integer.

Original bug: https://github.com/elastic/kibana/issues/184708

packages/kbn-unified-data-table/src/components/data_table_additional_display_settings.test.tsx

@@ -140,6 +140,42 @@ describe('UnifiedDataTableAdditionalDisplaySettings', function () {
 
       expect(onChangeSampleSizeMock).not.toHaveBeenCalled();
     });
+
+    it('should only render integers when a decimal value is provided', async () => {
+      const invalidDecimalValue = 6.11;
+      const validIntegerValue = 6;
+
+      const onChangeSampleSizeMock = jest.fn();
+
+      const component = mountWithIntl(
+        <UnifiedDataTableAdditionalDisplaySettings
+          maxAllowedSampleSize={500}
+          sampleSize={50}
+          onChangeSampleSize={onChangeSampleSizeMock}
+          rowHeight={RowHeightMode.custom}
+          rowHeightLines={10}
+          headerRowHeight={RowHeightMode.custom}
+          headerRowHeightLines={5}
+        />
+      );
+      const input = findTestSubject(component, 'unifiedDataTableSampleSizeInput').last();
+      expect(input.prop('value')).toBe(50);
+
+      await act(async () => {
+        input.simulate('change', {
+          target: {
+            value: invalidDecimalValue,
+          },
+        });
+      });
+
+      await new Promise((resolve) => setTimeout(resolve, 0));
+      component.update();
+
+      expect(
+        findTestSubject(component, 'unifiedDataTableSampleSizeInput').last().prop('value')
+      ).toBe(validIntegerValue);
+    });
   });
 
   describe('rowHeight', () => {

packages/kbn-unified-data-table/src/components/data_table_additional_display_settings.tsx

@@ -70,7 +70,7 @@ export const UnifiedDataTableAdditionalDisplaySettings: React.FC<
         return;
       }
 
-      const newSampleSize = Number(event.target.value);
+      const newSampleSize = parseInt(event.target.value, 10) ?? RANGE_MIN_SAMPLE_SIZE;
 
       if (newSampleSize >= MIN_ALLOWED_SAMPLE_SIZE) {
         setActiveSampleSize(newSampleSize);