Introduce Preset Register Specialized Emission
- Introduce EmissionOption trait
- Introduce PresetAnnotation & PresetRegAnnotation
- Enable the collection of Annotations in the Emitter
- Introduce collection mechanism for EmissionOptions in the Emitter
- Add PropagatePresetAnnotation transform to annotate register for emission and clean-up the useless reset tree (no DCE involved)
- Add corresponding tests spec and tester

Co-authored-by: Jack Koenig <koenig@sifive.com>

Fixes #219

* Adds AsyncResetType (similar to ClockType)
* Registers with reset signal of type AsyncResetType are async reset
  registers
* Registers with async reset can only be reset to literal values
* Add initialization logic for async reset registers

This should close #757. It should also allow for stop() and printf()
to be used with zero-width fields.

Closes #666.

Resolves #600

* Rename implict module "clk" input to "clock".
This doesn't rename all the "self-contained" test instances.
nor the memory "clk" enables,
nor the implict module "clk"s in the regress .fir files.

* Consistency: rename implict module "clk" input to "clock" in "self-contained" test instances.
This doesn't rename the memory "clk" enables, nor the implict module "clk"s in the regress .fir files.

* handle uninferred ports gracefully in RemoveCHIRRTL

memory port directions are not inferred during CInferMDir if not being used, so handle them properly in RemoveCHIRRTL

* fix CInferTypes