Use ChiselStage in Tests

This migrates the tests to Chisel 3.4/FIRRTL 1.4. This primarily
involves removing usages of deprecated methods including:

- Remove usages of Driver
- Use ChiselStage methods instead of BackendCompilationUtilities
  methods
- Use Dependency API for custom transforms
- Use extractCause to unpack StackError

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