Reduce padding in Modes dialog and make marquee less eager

Also, controlled by a flag, switch to one-row-per-tile. This flag is not intended to be advanced, but only used to compare both approaches, and eventually inline the one we prefer.

Bug: 366034002
Test: manual
Flag: android.app.modes_ui
Change-Id: I94a4467ebd572d17250d78b9ef772152f58caa77
diff --git a/packages/SystemUI/aconfig/systemui.aconfig b/packages/SystemUI/aconfig/systemui.aconfig
index 02e8cd6..00f69ed 100644
--- a/packages/SystemUI/aconfig/systemui.aconfig
+++ b/packages/SystemUI/aconfig/systemui.aconfig
@@ -149,6 +149,16 @@
 }
 
 flag {
+   name: "modes_dialog_single_rows"
+   namespace: "systemui"
+   description: "[Experiment] Display one entry per grid row in the Modes Dialog."
+   bug: "366034002"
+   metadata {
+        purpose: PURPOSE_BUGFIX
+   }
+}
+
+flag {
    name: "pss_app_selector_recents_split_screen"
    namespace: "systemui"
    description: "Allows recent apps selected for partial screenshare to be launched in split screen mode"