[SPARK-33223][SS][FOLLOWUP] Clarify the meaning of "number of rows dr…

…opped by watermark" in SS UI page

### What changes were proposed in this pull request?

This PR fixes the representation to clarify the meaning of "number of rows dropped by watermark" in SS UI page.

### Why are the changes needed?

`Aggregated Number Of State Rows Dropped By Watermark` says that the dropped rows are from the state, whereas they're not. We say "evicted from the state" for the case, which is "normal" to emit outputs and reduce memory usage of the state.

The metric actually represents the number of "input" rows dropped by watermark, and the meaning of "input" is relative to the "stateful operator". That's a bit confusing as we normally think "input" as "input from source" whereas it's not.

### Does this PR introduce _any_ user-facing change?

Yes, UI element & tooltip change.

### How was this patch tested?

Only text change in UI, so we know how thing will be changed intuitively.

Closes #30439 from HeartSaVioR/SPARK-33223-FOLLOWUP.

Authored-by: Jungtaek Lim (HeartSaVioR) <kabhwan.opensource@gmail.com>
Signed-off-by: Jungtaek Lim (HeartSaVioR) <kabhwan.opensource@gmail.com>

sql/core/src/main/scala/org/apache/spark/sql/streaming/ui/StreamingQueryStatisticsPage.scala

@@ -189,8 +189,8 @@ private[ui] class StreamingQueryStatisticsPage(parent: StreamingQueryTab)
 
       val graphUIDataForNumRowsDroppedByWatermark =
         new GraphUIData(
-          "aggregated-num-state-rows-dropped-by-watermark-timeline",
-          "aggregated-num-state-rows-dropped-by-watermark-histogram",
+          "aggregated-num-rows-dropped-by-watermark-timeline",
+          "aggregated-num-rows-dropped-by-watermark-histogram",
           numRowsDroppedByWatermarkData,
           minBatchTime,
           maxBatchTime,
@@ -230,11 +230,11 @@ private[ui] class StreamingQueryStatisticsPage(parent: StreamingQueryTab)
       <tr>
         <td style="vertical-align: middle;">
           <div style="width: 160px;">
-            <div><strong>Aggregated Number Of State Rows Dropped By Watermark {SparkUIUtils.tooltip("Aggregated number of state rows dropped by watermark.", "right")}</strong></div>
+            <div><strong>Aggregated Number Of Rows Dropped By Watermark {SparkUIUtils.tooltip("Accumulates all input rows being dropped in stateful operators by watermark. 'Inputs' are relative to operators.", "right")}</strong></div>
           </div>
         </td>
-        <td class={"aggregated-num-state-rows-dropped-by-watermark-timeline"}>{graphUIDataForNumRowsDroppedByWatermark.generateTimelineHtml(jsCollector)}</td>
-        <td class={"aggregated-num-state-rows-dropped-by-watermark-histogram"}>{graphUIDataForNumRowsDroppedByWatermark.generateHistogramHtml(jsCollector)}</td>
+        <td class={"aggregated-num-rows-dropped-by-watermark-timeline"}>{graphUIDataForNumRowsDroppedByWatermark.generateTimelineHtml(jsCollector)}</td>
+        <td class={"aggregated-num-rows-dropped-by-watermark-histogram"}>{graphUIDataForNumRowsDroppedByWatermark.generateHistogramHtml(jsCollector)}</td>
       </tr>
       // scalastyle:on
     } else {

sql/core/src/test/scala/org/apache/spark/sql/streaming/ui/UISeleniumSuite.scala

@@ -139,7 +139,7 @@ class UISeleniumSuite extends SparkFunSuite with WebBrowser with Matchers with B
             summaryText should contain ("Aggregated Number Of Total State Rows (?)")
             summaryText should contain ("Aggregated Number Of Updated State Rows (?)")
             summaryText should contain ("Aggregated State Memory Used In Bytes (?)")
-            summaryText should contain ("Aggregated Number Of State Rows Dropped By Watermark (?)")
+            summaryText should contain ("Aggregated Number Of Rows Dropped By Watermark (?)")
           }
         } finally {
           spark.streams.active.foreach(_.stop())