accept proxy address from intent

[xiaozhikang0916]

Accept proxy setting from intent's extra data

• Add SavedStateHandle in ProxyManagerViewModel to accept initial input param
• Mark MainActivity as singleInstance to receive any coming intent after it is started
• 2 unit test case for this new function

[xiaozhikang0916]

To wait for a synchronization of the uiState, which may be modified by init block and the deviceSettingsManager instance, I used a while-yield loop here, which may be not elegant. Any advise?