Fix build, remove TestModule.UTest from AmmInternalModule (#1389)

This fixes the issue
#1386:

```
> ./mill -i amm.repl[3.2.2].test
GITHUB REF None
fatal: no tag exactly matches 'cdeaa580bf128779686991a838623dd3a75af49b'
[296/296] amm.repl[3.2.2].test
java.lang.ClassNotFoundException: utest.runner.Framework
java.lang.ClassNotFoundException: utest.runner.Framework
    at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:476)
    at mill.api.ClassLoader$$anon$1.findClass(ClassLoader.scala:47)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:594)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:527)
    at mill.testrunner.TestRunner$.framework(TestRunner.scala:412)
    at mill.testrunner.TestRunner$.$anonfun$main$2(TestRunner.scala:252)
    at mill.testrunner.TestRunner$.$anonfun$runTestFramework$2(TestRunner.scala:326)
    at mill.util.Jvm$.inprocess(Jvm.scala:30)
    at mill.testrunner.TestRunner$.runTestFramework(TestRunner.scala:320)
    at mill.testrunner.TestRunner$.main(TestRunner.scala:258)
    at mill.testrunner.TestRunner.main(TestRunner.scala)
1 targets failed
amm.repl[3.2.2].test Test execution failed.
```

The issue is, that `amm.repl[3.2.2]` (defined by `ReplModule` which
extends `AmmModule` which itself extends `AmmoniteInternalModule`) is
itself a `TestModule.UTest`. That means, it already has a `test` target,
so that the resolver will never search for a submodule that implements a
`defaultCommand`.

After removing `TestModule.UTest` from `AmmoniteInternalModule`, the cli
call properly resolves to `amm.repl[3.2.2].test.test`.

I'm curious to know, why this even compiled. We end up with two class
members `test`, one `def` with the test target, and one `object` with
the test sub-module.

Pull request: #1389

build.sc

@@ -116,7 +116,7 @@ object Deps {
   val utest = ivy"com.lihaoyi::utest:0.8.1"
 }
 
-trait AmmInternalModule extends CrossSbtModule with Bloop.Module with TestModule.Utest{
+trait AmmInternalModule extends CrossSbtModule with Bloop.Module {
   // We need it to be a Boolean, not T[Boolean]
   def isCrossFullScalaVersion: Boolean = false
   def crossFullScalaVersion = T { isCrossFullScalaVersion }
@@ -150,7 +150,7 @@ trait AmmInternalModule extends CrossSbtModule with Bloop.Module with TestModule
       ivy"$scalaO:scala-library:$scalaV"
     )
   }
-  trait Tests extends super.Tests with TestModule.Utest{
+  trait AmmTests extends super.Tests with TestModule.Utest{
     def ivyDeps = super.ivyDeps() ++ Agg(Deps.utest)
     def forkArgs = Seq("-Xmx2g", "-Dfile.encoding=UTF8")
   }
@@ -283,7 +283,7 @@ class TerminalModule(val crossScalaVersion: String) extends AmmModule{
       Deps.sourcecode
     )
   }
-  object test extends Tests{
+  object test extends AmmTests{
     def ivyDeps = super.ivyDeps() ++ Agg(Deps.sourcecode)
   }
 }
@@ -361,7 +361,7 @@ object amm extends Cross[MainModule](fullCrossScalaVersions:_*){
         transitiveSourceJars()
     }
 
-    object test extends Tests
+    object test extends AmmTests
   }
 
   object interp extends Cross[InterpModule](fullCrossScalaVersions:_*){
@@ -463,7 +463,7 @@ object amm extends Cross[MainModule](fullCrossScalaVersions:_*){
     )
     def compileIvyDeps = super.compileIvyDeps() ++ (if(isScala3(crossScalaVersion)) Agg.empty[Dep] else Agg(Deps.scalaReflect(scalaVersion())))
 
-    object test extends Tests with AmmDependenciesResourceFileModule {
+    object test extends AmmTests with AmmDependenciesResourceFileModule {
       def crossScalaVersion = ReplModule.this.crossScalaVersion
       def scalaVersion = ReplModule.this.scalaVersion
       def dependencyResourceFileName = "amm-test-dependencies.txt"
@@ -578,7 +578,7 @@ class MainModule(val crossScalaVersion: String) extends AmmModule {
       }
   }
 
-  object test extends super.Tests {
+  object test extends AmmTests {
     def moduleDeps = super.moduleDeps ++ Seq(amm.compiler().test, amm.repl().test)
     def ivyDeps = super.ivyDeps() ++ Agg(
       Deps.scalaJava8Compat
@@ -650,7 +650,7 @@ class IntegrationModule(val crossScalaVersion: String) extends AmmInternalModule
         Agg.empty
     )
   }
-  object test extends Tests {
+  object test extends AmmTests {
     def testLauncher = T {
       if (scala.util.Properties.isWin)
         amm().launcher().path.toString
@@ -672,7 +672,7 @@ class SshdModule(val crossScalaVersion: String) extends AmmModule{
     Deps.sshdCore,
     Deps.bcprovJdk15on
   )
-  object test extends Tests {
+  object test extends AmmTests {
     def ivyDeps = super.ivyDeps() ++ Agg(
       // slf4j-nop makes sshd server use logger that writes into the void
       Deps.slf4jNop,