Auto merge of #15368 - szeged:get_availability, r=nox

Implement GetAvailability for Bluetooth

<!-- Please describe your changes on the following line: -->
This implements the [getAvailability](https://webbluetoothcg.github.io/web-bluetooth/#dom-bluetooth-getavailability) function from the spec.

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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components/bluetooth/lib.rs

@@ -246,13 +246,16 @@ impl BluetoothManager {
                 },
                 BluetoothRequest::Test(data_set_name, sender) => {
                     let _ = sender.send(self.test(data_set_name));
-                }
+                },
                 BluetoothRequest::SetRepresentedToNull(service_ids, characteristic_ids, descriptor_ids) => {
                     self.remove_ids_from_caches(service_ids, characteristic_ids, descriptor_ids)
-                }
+                },
                 BluetoothRequest::IsRepresentedDeviceNull(id, sender) => {
                     let _ = sender.send(!self.device_is_cached(&id));
-                }
+                },
+                BluetoothRequest::GetAvailability(sender) => {
+                    let _ = sender.send(self.get_availability());
+                },
                 BluetoothRequest::Exit => {
                     break
                 },
@@ -924,4 +927,9 @@ impl BluetoothManager {
         // TODO: Implement this when supported in lower level
         return Err(BluetoothError::NotSupported);
     }
+
+    // https://webbluetoothcg.github.io/web-bluetooth/#dom-bluetooth-getavailability
+    fn get_availability(&mut self) -> BluetoothResponseResult {
+        Ok(BluetoothResponse::GetAvailability(self.get_adapter().is_ok()))
+    }
 }