Move tests for sendBeacon to a separate dedicated directory for clearer ownership

third_party/WebKit/LayoutTests/VirtualTestSuites

 [
   {
     "prefix": "color_space",
     "base": "fast/canvas/color-space",
     "args": ["--enable-color-correct-rendering",
              "--enable-true-color-rendering"]
   },
   {
     "prefix": "gpu",
     "base": "fast/canvas",
@@ skipping 72 matching lines @@
     "base": "http/tests/serviceworker/webexposed",
     "args": ["--stable-release-mode"]
   },
   {
     "prefix": "stable",
     "base": "http/tests/navigation",
     "args": ["--stable-release-mode"]
   },
   {
     "prefix": "stable",
+    "base": "http/tests/sendbeacon",
+    "args": ["--stable-release-mode"]
+  },
+  {
+    "prefix": "stable",
     "base": "animations-unprefixed",
     "args": ["--stable-release-mode"]
   },
   {
     "prefix": "stable",
     "base": "media/stable",
     "args": ["--stable-release-mode"]
   },
   {
     "prefix": "disable-spinvalidation",
@@ skipping 257 matching lines @@
     "prefix": "mojo-localstorage",
     "base": "storage/domstorage/localstorage",
     "args": ["--mojo-local-storage"]
   },
   {
     "prefix": "print_browser",
     "base": "print_testharness",
     "args": ["--enable-print-browser"]
   }
 ]