Publish unidoc as ScalaDoc in chisel project (backport #2595) (#2598)

* Publish unidoc as ScalaDoc in chisel project (#2595)

This makes it such that we can stop hosting ScalaDoc on the Chisel
website, instead just pointing to the latest docs on javadoc.io

(cherry picked from commit 8b9f3d7)

# Conflicts:
#	build.sbt

* Resolve backport conflicts

Co-authored-by: Jack Koenig <koenig@sifive.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

build.sbt

@@ -219,6 +219,10 @@ lazy val chisel = (project in file(".")).
     ),
     libraryDependencies += defaultVersions("treadle") % "test",
     Test / scalacOptions += "-P:chiselplugin:genBundleElements",
+    // Forward doc command to unidoc
+    Compile / doc := (ScalaUnidoc / doc).value,
+    // Include unidoc as the ScalaDoc for publishing
+    Compile / packageDoc / mappings := (ScalaUnidoc / packageDoc / mappings).value,
     scalacOptions in Test ++= Seq("-language:reflectiveCalls"),
     scalacOptions in Compile in doc ++= Seq(
       "-diagrams",