Add AlignmentLineOffset layout widget

The CL adds the AlignmentLineOffset layout widget, which positions its
only child within itself according to before and after offsets from an
alignment line of the child. AlignmentLineOffset has a wrap content
behavior - it tries to be as small as possible while satisfying the
requested offsets.

Bug: 138939507
Test: ran AlignmentLineTest
Change-Id: Ie642c5b22068a62437efe9fec66be9c58ddb6e4d

diff --git a/ui/ui-layout/api/restricted_current.txt b/ui/ui-layout/api/restricted_current.txt
index 732a954..cad24c3 100644
--- a/ui/ui-layout/api/restricted_current.txt
+++ b/ui/ui-layout/api/restricted_current.txt

@@ -20,6 +20,11 @@
     enum_constant public static final androidx.ui.layout.Alignment TopRight;
   }
 
+  public final class AlignmentLineKt {
+    ctor public AlignmentLineKt();
+    method public static void AlignmentLineOffset(androidx.ui.core.AlignmentLine alignmentLine, androidx.ui.core.Dp before = 0.dp, androidx.ui.core.Dp after = 0.dp, kotlin.jvm.functions.Function0<kotlin.Unit> children);
+  }
+
   public final class AspectRatioKt {
     ctor public AspectRatioKt();
     method public static void AspectRatio(float aspectRatio, kotlin.jvm.functions.Function0<kotlin.Unit> children);