bluez/client: move state management to global BlueZ manager

This fixes a number of bugs by moving the `BleakClient` state management
to the new global BlueZ manager object.

- Calling "GetManagedObjects" each time we connected caused performance
  issues. Fixes #500.
- Calling "ConnectDevice" didn't work as expected and has been removed/
  Fixes #806.
- BleakClient didn't handle "InterfacesRemoved" which resulted in an
  invalid service dictionary in some cases. Fixes #882.

CHANGELOG.rst

@@ -38,7 +38,14 @@ Fixed
 
 * Documentation fixes.
 * On empty characteristic description from WinRT, use the lookup table instead of returning empty string.
+* Fixed performance issues in BlueZ backend caused by calling "GetManagedObjects" each time a
+  ``BleakScanner`` scans or ``BleakClient`` is connected. Fixes #500.
+* Fixed not handling "InterfacesRemoved" in ``BleakClient`` in BlueZ backend. Fixes #882.
 
+Removed
+-------
+
+* Removed fallback to call "ConnectDevice" when "Connect" fails in Bluez backend. Fixes #806.
 
 `0.14.3`_ (2022-04-29)
 ======================