Configuration for how much of the project to build

At the moment, HLS builds only the files that are open in the editor by default (and their dependencies). We have the `checkProject` option, which instead builds all the files in the current _component_.

Especially once proper multi-component support is finished, it seems to me that there are actually several levels of aggressiveness that you might want.
1. Build only the files open in the editor
2. Build all the files in the current component
3. Build all the files in all the components in the current package
4. Build all the files in all the components in all the packages in the project

So I wonder if we should replace `checkProject` with a new option (`buildAggressiveness`?) with four alternatives:
1. `open-files`
2. `current-component`
3. `current-package`
4. `all-packages`