Add lockdown mode activation to lockdown-mode pallet's `GenesisConfig` (#176)

* add activating lockdown mode to GenesisConfig

* add activating lockdown mode to test ext

* add tests for activating lockdown mode in GenesisConfig

* cargo fmt -p pallet-lockdown-mode

* fix linting

* add activated to benchmark

* removing, as this is already in another test

* setting initial state to true, therefore no longer need to manually change state

* rename activated in genesisConfig to initial_status