ImportedDefinitionExtModule does not include secret ports (bores)

**Type of issue**: Bug Report

**Please provide the steps to reproduce the problem:**

**What is the current behavior?**

If I have a module which has bored (secret) ports, and I create an ImportedDefinitionExtModule from it, those ports are not included in the extmodule

**What is the expected behavior?**

Those bored ports should be included in the extmodule .fir. Note that since it might be hard to actually *drive* them since they can't really be marked @public, this might just mean you get firrtl error about invalid / undriven ports.

**Please tell us about your environment:**

**Other Information**

**What is the use case for changing the behavior?**

Should realize before .sv simulation time that some ports are undriven