Auto save the file before compilation

[Dragonado]

Currently, when you click on the "run test cases" button, the extension compiles the previously saved file and runs the test cases against that. So if you edit the solution file but not save it, then the extension won't consider the new file while running test cases.

This is not intended behaviour on the user side. They definitely meant to save the file and then run the test cases. So we can automate this, we just have to use the VSCode API to save the file before compiling the file.