Deprecate ChiselStage$.elaborate

[seldridge]

Deprecate ChiselStage$.elaborate as this exposes internal Chisel APIs, namely "chisel3.internal.firrtl.Circuit". Replace usages of this in tests with emitCHIRRTL.

[jackkoenig]

Suggested change

	@deprecated(
	"this exposes the internal Chisel circuit which was not supposed to be public---use either ChiselStage.convert or ChiselStage.emitCHIRRTL instead ",
	"Chisel 5.0"
	)
	@deprecated(
	"this exposes the internal Chisel circuit which was not supposed to be public--use either ChiselStage.convert or ChiselStage.emitCHIRRTL instead",
	"Chisel 5.0"
	)

Minor nit on the message, feel free to ignore

[seldridge]

The use of a fixed-width em-dash was intentional as opposed to a fixed-width en-dash which would not be appropriate. I could use alternative punctuation, though. The space was unintentional. I'll remove that.

[mwachs5]

seems like we have lots of tests where we don't actually care about the emission, and just want to see if we can successfully elaborate. Could we make something like testElaborate or checkElaborate just return Unit or true/false? Does emitChirrtl always emit a file, which could be annoying...

[seldridge]

ChiselStage$.emitCHIRRTL or ChiselStage$.convert do not write any files. I considered adding a test-only elaborate method to do this, but it seemed unnecessary given that there was an existing method which we could re-use here.