Improve test utils to run code gen tasks in a compiler plugin

[pubudu91]

In the current BCompileUtil test utils, the methods don't seem to execute code gen tasks of a compiler plugin when compiling. The requirement was the following:

• I have a Ballerina package which also has a compiler plugin which includes a code gen task.
• I have an integration test suite written using the above mentioned test utils.
• But since the compile utils don't run the code gen task, my code gen task is not getting tested and the test coverage drops.

[anupama-pathirage]

We are closing this issue due to inactivity. If you need further assistance or have additional input, feel free to reopen it. Thank you for helping us maintain a relevant and focused issue list!