Implement property for explicit jvmTarget for script definition...

Apply the property to the default JSR-223 script taking the value from
java.specification.version property, so effectively implementing
jvmTarget detection from current VM.
Also drop enforcing of target 1.8, using common default.
#KT-49329 fixed
#KT-40497 fixed

libraries/scripting/jvm/src/kotlin/script/experimental/jvm/jvmScriptCompilation.kt

@@ -101,6 +101,8 @@ val JvmScriptCompilationConfigurationKeys.jdkHome
             getSourceProperties = { get(ScriptCompilationConfiguration.hostConfiguration) }
         )
 
+val JvmScriptCompilationConfigurationKeys.jvmTarget by PropertiesCollection.key<String>()
+
 @Suppress("unused")
 val ScriptCompilationConfigurationKeys.jvm
     get() = JvmScriptCompilationConfigurationBuilder()