Bump emitted FIRRTL to 5.1.0 (#4841)

Bump the emitted FIRRTL version to 5.1.0.  This is done because we want to
start using the new `{{SimulationTime}}` printf construct.  This is a
major change to FIRRTL (as it is a backwards incompatible change) and
therefore we have to go through the major bump.

The minor bump needs to stay at "1" because we are still emitting things
which are not in the FIRRTL spec, e.g., Path ops.

Signed-off-by: Schuyler Eldridge <[email protected]>

Author: seldridge

core/src/main/scala/chisel3/internal/firrtl/Serializer.scala

@@ -19,7 +19,7 @@ private[chisel3] object Serializer {
   private val Indent = "  "
 
   // The version supported by the serializer.
-  val version = "4.2.0"
+  val version = "5.1.0"
 
   def getRef(id: HasId, sourceInfo: SourceInfo): Arg =
     id.getOptionRef.getOrElse {

src/test/scala-2/circtTests/stage/ChiselStageSpec.scala

@@ -1087,7 +1087,7 @@ class ChiselStageSpec extends AnyFunSpec with Matchers with chiselTests.LogUtils
 
       val text = ChiselStage.emitCHIRRTL(new ChiselStageSpec.Foo(hasDontTouch = true))
       info("found a version string")
-      text should include("FIRRTL version 4.2.0")
+      text should include("FIRRTL version 5.1.0")
       info("found an Annotation")
       text should include("firrtl.transforms.DontTouchAnnotation")
       info("found a circuit")