Reset nwConfig before refreshing for a new one

[garg3133]

Before re-requireing the Nightwatch config file, we should always reset the nwConfig from workspaceState, otherwise if there is some error in the config file or the config file has altogether been deleted, Nightwatch VSCode extension will just keep on showing the old environments in the Environments Panel and no information of the error will be transmitted to the user in any way, which is quite misleading and bad UX, as the extension will stop working and the user wouldn't know why.

Ex. in the development mode, if I delete the nightwatch.conf.js file, it shows error in the Debug Console of my development environment:

but the environments in the Environments Panel remains the same with no error/warning being transmitted to the user:

Reseting the nwConfig before requireing a new one would at least reset the envs in Environments Panel and in case there is an error, we should show it to the user (maybe in form of a pop-up?).