Use gap closing settings with palette drag and drop fill

Per the Krita Artists request [here](https://krita-artists.org/t/allow-drag-and-drop-color-fill-palette-color-box-to-use-the-fill-tool-settings/29030/9?u=yrh), this patch makes the palette color drag-and-drop to fill feature honor gap closing settings of the flood fill tool.

The similar code is present in `kis_tool_fill.cc` already.

Test Plan
---------

1. You can use the test image in `libs/image/tests/data/close_gap_low.png`.
2. Select the fill tool and set the close gap size of 5.
3. Drag a color from the palette docker to the canvas and drop into any region with small gaps on the sides.
4. The fill should stop before spilling.

Other:

- Gap size 0 should behave as a regular fill.
- Fast mode should be disabled for non-zero gap size.

I don't think there's an automated test for this.

Formalities Checklist
--------------------- 

- [x] I confirmed this builds.
- [x] I confirmed Krita ran and the relevant functions work.
- [x] I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!)
- [x] I made sure my commits build individually and have good descriptions as per [KDE guidelines](https://community.kde.org/Policies/Commit_Policy).
- [x] I made sure my code conforms to the standards set in the HACKING file.
- [x] I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per [KDE Licensing Policy](https://community.kde.org/Policies/Licensing_Policy).

_**Reminder: the reviewer is responsible for merging the patch, this is to ensure at the least two people can build the patch. In case a patch breaks the build, both the author and the reviewer should be contacted to fix the build.**_
_**If this is not possible, the commits shall be reverted, and a notification with the reasoning and any relevant logs shall be sent to the mailing list, [email protected].**_

libs/ui/KisView.cpp

@@ -867,6 +867,7 @@ void KisView::dropEvent(QDropEvent *event)
             const int grow = configGroup.readEntry("growSelection", 0);
             const bool stopGrowingAtDarkestPixel = configGroup.readEntry<bool>("stopGrowingAtDarkestPixel", false);
             const int feather = configGroup.readEntry("featherAmount", 0);
+            const int closeGap = configGroup.readEntry("closeGapAmount", 0);
             QString sampleLayersMode = configGroup.readEntry("sampleLayersMode", "");
             if (sampleLayersMode.isEmpty()) {
                 if (configGroup.readEntry("sampleMerged", false)) {
@@ -970,6 +971,7 @@ void KisView::dropEvent(QDropEvent *event)
                                          opacitySpread == 100 &&
                                          useSelectionAsBoundary == false &&
                                          !antiAlias && grow == 0 && feather == 0 &&
+                                         closeGap == 0 &&
                                          sampleLayersMode == "currentLayer";
 
                 FillProcessingVisitor *visitor = new FillProcessingVisitor(referencePaintDevice,
@@ -987,6 +989,7 @@ void KisView::dropEvent(QDropEvent *event)
                 }
                 visitor->setFillThreshold(threshold);
                 visitor->setOpacitySpread(opacitySpread);
+                visitor->setCloseGap(closeGap);
                 visitor->setAntiAlias(antiAlias);
                 visitor->setUseCustomBlendingOptions(useCustomBlendingOptions);
                 if (useCustomBlendingOptions) {