Auto merge of #27429 - asajeffrey:webxr-user-intent-pref, r=Manishearth

Add a pref to indicate user intent to enter webxr

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Add a pref to indicate that the user has indicated intent to enter webxr.

---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes do not require tests because it's a command-line pref

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components/config/prefs.rs

@@ -301,6 +301,8 @@ mod gen {
                         enabled: bool,
                     },
                     sessionavailable: bool,
+                    #[serde(rename = "dom.webxr.unsafe-assume-user-intent")]
+                    unsafe_assume_user_intent: bool,
                 },
                 worklet: {
                     blockingsleep: {