Move DisableFold option to ConstantPropagation

[sequencer]

Get rid of binary compatibility issue for #2150, should get this merged in 1.5.

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?
• [x] Did you delete any extraneous printlns/debugging code?
• [x] Did you specify the type of improvement?
• [x] Did you state the API impact?
• [x] Did you specify the code generation impact?
• [x] Did you request a desired merge strategy?
• [x] Did you add text to be included in the Release Notes for this change?

Type of Improvement

• code refactoring

API Impact

remove

Backend Code Generation Impact

none

Desired Merge Strategy

• Rebase: You will rebase the PR onto master and it will be merged with a merge commit.

Release Notes

no more DisableFold object.

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?