fix: remove webpackCompilationComplete handler correctly on prepare
fix: remove webpackCompilationComplete handler correctly on prepare

Commands using prepare of project (and using SK) should remove their handlers for webpackCompilerService's `webpackCompilationComplete` event. This is not happening and whenever we start new prepartion of the project, we attach new handler.

This causes issues when running on device in Sidekick, closing the current app, open it again and try to livesync a change - we have many handlers for prepareReadyEvent and this causes multiple livesync operations.

NathanaelA/nativescript-cli,NativeScript/nativescript-cli,NativeScript/nativescript-cli,NathanaelA/nativescript-cli,NathanaelA/nativescript-cli,NativeScript/nativescript-cli,NativeScript/nativescript-cli,NathanaelA/nativescript-cli