Add MUnit test framework

main/src/main/scala/sbt/Defaults.scala

@@ -1184,7 +1184,7 @@ object Defaults extends BuildCommon {
       Seq(
         testFrameworks :== {
           import sbt.TestFrameworks._
-          Seq(ScalaCheck, Specs2, Specs, ScalaTest, JUnit)
+          Seq(ScalaCheck, Specs2, Specs, ScalaTest, JUnit, MUnit)
         },
         testListeners :== Nil,
         testOptions :== Nil,

sbt/src/sbt-test/tests/munit/build.sbt

@@ -5,6 +5,5 @@ lazy val munit = "org.scalameta" %% "munit" % "0.7.22"
 lazy val root = (project in file("."))
   .settings(
     Compile / scalacOptions += "-Yrangepos",
-    libraryDependencies += munit % Test,
-    testFrameworks += new TestFramework("munit.Framework"),
+    libraryDependencies += munit % Test
   )

testing/src/main/scala/sbt/TestFramework.scala

@@ -26,6 +26,7 @@ object TestFrameworks {
   val Specs2 =
     TestFramework("org.specs2.runner.Specs2Framework", "org.specs2.runner.SpecsFramework")
   val JUnit = TestFramework("com.novocode.junit.JUnitFramework")
+  val MUnit = TestFramework("munit.Framework")
 }
 
 final class TestFramework(val implClassNames: String*) extends Serializable {