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/jsr223/src/kotlin/script/experimental/jsr223/KotlinJsr223DefaultScript.kt

@@ -14,6 +14,8 @@ import kotlin.script.experimental.api.ScriptCompilationConfiguration
 import kotlin.script.experimental.api.ScriptEvaluationConfiguration
 import kotlin.script.experimental.api.refineConfiguration
 import kotlin.script.experimental.api.refineConfigurationBeforeEvaluate
+import kotlin.script.experimental.jvm.jvm
+import kotlin.script.experimental.jvm.jvmTarget
 import kotlin.script.experimental.jvmhost.jsr223.configureProvidedPropertiesFromJsr223Context
 import kotlin.script.experimental.jvmhost.jsr223.importAllBindings
 import kotlin.script.experimental.jvmhost.jsr223.jsr223
@@ -66,6 +68,11 @@ object KotlinJsr223DefaultScriptCompilationConfiguration : ScriptCompilationConf
         jsr223 {
             importAllBindings(true)
         }
+        jvm {
+            System.getProperty("java.specification.version")?.let {
+                jvmTarget(it)
+            }
+        }
     }
 )