Add Driver Compatibility Layer

This includes phases necessary to provide backwards compatibility with
the old Chisel3 Driver. These are placed in a DriverCompatibility
object inside chisel3.stage.phases. The following four phases are
included:
  - AddImplicitOutputFile (from a TopNameAnnotation)
  - AddImplicitOutputAnnotationFile phase
  - DisableFirrtlStage (to disable ChiselStage running FirrtlStage)
  - MutateOptionsManager (to update options after ChiselStage)
  - ReEnableFirrtlStage (to renable FirrtlStage if needed)

Additionally, this adds a view of a ChiselExecutionResult for
providing the legacy return type of the Chisel Driver.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>