Improve ctrl + c handling

[DimitarTachev]

Is your feature request related to a problem? Please describe.
Currently, the CLI cannot be easily killed with ctrl + c.

Describe the solution you'd like
Stop handling the SIGINT signals and let the nodejs do the job.

Describe alternatives you've considered
Extract a common helpers for managing the timeouts, intervals and child processes and keep the exit logic in a single place.

[rosen-vladimirov]

The issue should be fixed in latest next version of nativescript CLI. To get the full benefits of it, you can install CLI's next version by executing npm i -g nativescript@next.
The new approach of handling Ctrl + C is described in the related PR. The main concept is that now CLI does not handle SIGINT signal. Instead, it starts a new child process that will cleanup the resources once CLI's process dies. As the child process is detached and executes most of its work after CLI's dead, you can pass --cleanupLogFile <path to file> where the logs of the execution will be stored. The child process will execute the cleanup actions, write information to the specified file (in case the cleanupLogFile option is not passed, it will not create log) and after that it will exit.