Enable Passing Objects to --custom-transforms/-fct

[seldridge]

This lets a user pass an object (with a trailing $) as a command line custom transform, e.g., this lets a user do the following:

firrtl -i Foo.fir -fct firrtl.passes.InferTypes$

Dependencies

• prerequisites: [https://github.com/Remove Deprecated Driver chisel#1475, https://github.com/Use Dependency in RunFirrtlTransformAnnotation #1697]

Contributor Checklist

• Did you add Scaladoc to every public function/method?
• Did you update the FIRRTL spec to include every new feature/behavior?
• Did you add at least one test demonstrating the PR?
• Did you delete any extraneous printlns/debugging code?
• Did you specify the type of improvement?
• Did you state the API impact?
• Did you specify the code generation impact?
• Did you request a desired merge strategy?
• Did you add text to be included in the Release Notes for this change?

Type of Improvement

• new feature/API

API Impact

Pure API expansion of the FIRRTL command line interface.

Backend Code Generation Impact

None

Desired Merge Strategy

• Squash: The PR will be squashed and merged (choose this if you have no preference.

Release Notes

Reviewer Checklist (only modified by reviewer)

• Did you add the appropriate labels?
• Did you mark the proper milestone (1.2.x, 1.3.0, 1.4.0) ?
• Did you review?
• Did you check whether all relevant Contributor checkboxes have been checked?
• Did you mark as Please Merge?