Device manager - rename session (PSG-528) (#9282)

* split heading into component

* switch between editing and view

* style file

* basic tests

* style device rename component

* add loading state

* kind of handle missing current device in drilled props

* use local loading state, add basic error message

* integration-ish test rename

* tidy

* fussy import ordering

* strict errors

test/components/views/settings/devices/CurrentDeviceSection-test.tsx

@@ -36,6 +36,7 @@ describe('<CurrentDeviceSection />', () => {
         device: alicesVerifiedDevice,
         onVerifyCurrentDevice: jest.fn(),
         onSignOutCurrentDevice: jest.fn(),
+        saveDeviceName: jest.fn(),
         isLoading: false,
         isSigningOut: false,
     };