Debug: Start without debugging cmd should always use current file

[ramya-rao-a]

Debug: Start without Debugging is the command to use to simply run the current file rather than debugging.

This works just fine just fine in the below cases:

• No launch.json file or it is empty
• The currently selected debug configuration in launch.json has the program attribute pointing to a file.

This falls back to debugging when the program attribute in the currently selected debug configuration points to a directory. This is because go run needs a file.

In such cases, we should use the file open in the currently active editor instead of falling back to debugging the package.

PRs are most welcome to fix this.
Code Pointers:

• Build and Debug extension
• Update resolveDebugConfiguration in goDebugConfiguration.ts file to return a new property called currentFile. This should have the path to file open in the active editor.
• Debug the debugger
• Update the go run call at https://github.com/Microsoft/vscode-go/blob/master/src/debugAdapter/goDebug.ts#L317 to use the value from the currentFile property if the program property does not point to a file itself

[ramya-rao-a]

This feature is now available in the latest version of the Go extension (0.8.0)
Thanks @brycekahle!