Auto merge of #18890 - glennw:update-wr-clip-text-aa, r=jdm

Update WR (details below):

* Add support for clip masks on text runs.
* Fix atomic ordering of items with multiple shadows.
* Update to bincode + ipc-channel with optimizations.
* Fix some plane splitting precision errors.
* Improve the anti-aliasing quality significantly.
* Add internal ClipChain support.
* Fix diacritic glyphs on Linux.

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tests/wpt/metadata-css/compositing-1_dev/html/mix-blend-mode-intermediate-element-overflow-hidden-and-border-radius.htm.ini

@@ -0,0 +1,6 @@
+[mix-blend-mode-intermediate-element-overflow-hidden-and-border-radius.htm]
+  type: reftest
+  expected:
+    if os == "linux": FAIL
+  bug: https://github.com/servo/webrender/issues/1776
+

tests/wpt/metadata-css/css-transforms-1_dev/html/transform-3d-rotateY-stair-below-001.htm.ini

@@ -0,0 +1,5 @@
+[transform-3d-rotateY-stair-below-001.htm]
+  type: reftest
+  expected: FAIL
+  bug: https://github.com/servo/webrender/issues/1776
+