Fix emit{Firrtl,Verilog} for CustomFileEmission

Change ChiselStage helper methods for emitting FIRRTL (emitFirrtl) and
Verilog (emitVerilog) to look for Circuit and Verilog annotations
instead of DeletedAnnotations. This is needed after migrating to the
CustomFileEmission mixin in FIRRTL where FIRRTL will no longer delete
emitter annotations.

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