bluetooth: Fix BLE discovery not working issue on MacOS

In the sequence of
BluetoothLowEnergyAdapterApple::RequestSystemPermission followed by
BluetoothLowEnergyAdapterApple::LazyInitialize,
low_energy_discovery_manager_ is not linked with the proper
CentralManager, and it results in no BLE devices in BLE discovery
session. This CL fixes the issue by properly set the CentralManager
for low_energy_discovery_manager_ during lazy initialization.

Bug: 349393380
Change-Id: Ibac58c22e8d9c5f2f46f815b414dd9b74dfb79ee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5656271
Auto-Submit: Jack Hsieh <[email protected]>
Reviewed-by: Nina Satragno <[email protected]>
Commit-Queue: Nina Satragno <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1319841}

device/bluetooth/bluetooth_low_energy_adapter_apple.mm

@@ -254,9 +254,8 @@
     low_energy_central_manager_ = [[CBCentralManager alloc]
         initWithDelegate:low_energy_central_manager_delegate_
                    queue:dispatch_get_main_queue()];
-    low_energy_discovery_manager_->SetCentralManager(
-        low_energy_central_manager_);
   }
+  low_energy_discovery_manager_->SetCentralManager(low_energy_central_manager_);
 
   low_energy_peripheral_manager_ = [[CBPeripheralManager alloc]
       initWithDelegate:low_energy_peripheral_manager_delegate_