Add clashRulesWithTop to set a specific top entity and module

[techninja1008]

This changeset refactors out the logic of clashRules into a clashRulesWithTop function that allows specification of a top module and entrypoint. clashRules is kept with the same signature and heuristic to determine those extra arguments in the simple cases.

Specifically, I've found for my use case that the isModuleName heuristic doesn't work as I compile through stack, and I need the ability to set custom values for clashTopName.

[gergoerdi]

Can you share the complete example where the isModuleName-based heuristic doesn't work?

[techninja1008]

In order for the clash compilation to work successfully inside stack, I have to pass a path to my module rather than a module name, otherwise the initial call to clash for dep-makefile fails and complains that the module doesn't exist. This then breaks the heuristic, as the module name is not Main but the passed file is a path and not a module.

I'm actually not sure why this breakage actually happens, and so far I've only been able to determine it's caused by not passing a HDL option when calling clash.