Test reporter fixes (#1597)

* Fix error message when an invalid test reporter is supplied in Gradle
* Fix Gradle property name in docs
* Fix Gradle property name in tasks
* Introduce `TestReporter.default`, and use it in places where default
is applied
* Remove calls to `convention()`; this is not required because the input
is optional anyways.

pkl-commons-cli/src/main/kotlin/org/pkl/commons/cli/CliTestOptions.kt

@@ -22,5 +22,5 @@ class CliTestOptions(
   val overwrite: Boolean = false,
   val junitAggregateReports: Boolean = false,
   val junitAggregateSuiteName: String = "pkl-tests",
-  val reporter: TestReporter = TestReporter.SPEC,
+  val reporter: TestReporter = TestReporter.default,
 )

pkl-commons-cli/src/main/kotlin/org/pkl/commons/cli/TestReporter.kt

@@ -17,5 +17,9 @@ package org.pkl.commons.cli
 
 enum class TestReporter {
   SPEC,
-  MINIMAL,
+  MINIMAL;
+
+  companion object {
+    @JvmStatic val default: TestReporter = SPEC
+  }
 }

pkl-commons-cli/src/main/kotlin/org/pkl/commons/cli/commands/TestOptions.kt

@@ -57,7 +57,7 @@ class TestOptions : OptionGroup() {
     option(names = arrayOf("--test-reporter"), help = "Which test reporter to use for CLI output.")
       .enum<TestReporter> { it.name.lowercase() }
       .single()
-      .default(TestReporter.SPEC)
+      .default(TestReporter.default)
 
   val cliTestOptions: CliTestOptions by lazy {
     CliTestOptions(