Bump accesskit version and patch egui to use updated accesskit (#42402)

We need to bump the accesskit version in order to use
[subtrees](https://docs.rs/accesskit/latest/accesskit/struct.Node.html#method.tree_id),
which are required to join the servo tree into the embedder tree.
We need to patch egui for servoshell, as we're waiting for them to land
the patch bumping their version of accesskit.
Once https://github.com/emilk/egui/pull/7850 lands and a new version of
egui is pushed out, we'll be able to remove the patch.

Testing: No tests.
Fixes: Part of #4344

Signed-off-by: Alice Boxhall <alice@igalia.com>

deny.toml

@@ -109,7 +109,12 @@ skip = [
     "itertools",
 
     # Duplicated by egui
+    "foldhash",
+    "windows-collections",
+    "windows-future",
+    "windows-numerics",
     "windows-strings",
+    "windows-threading",
 
     # Duplicated by egui-file-dialog
     "windows",
@@ -221,4 +226,9 @@ skip = [
 
 # github.com organizations to allow git sources for
 [sources.allow-org]
-github = ["servo"]
+github = [
+    "servo",
+
+    # Temporarily needed by servoshell: see root Cargo.toml
+    "emilk",
+]