Support ScriptEngine#eval(String, Bindings) in ScriptTemplateView

Supporting ScriptEngine#eval(String, Bindings) when no render function
is specified allows to support use cases where script templates are
simply evaluating a script expression with an even more simplified
configuration.

This improvement also makes it possible to use script engines that
do not implement Invocable.

Issue: SPR-15115

spring-webmvc/src/test/resources/org/springframework/web/servlet/view/script/kotlin/eval.kts

@@ -0,0 +1,4 @@
+// TODO Improve syntax when KT-15125 will be fixed
+"""${bindings["header"]}
+<p>${bindings["hello"]} ${bindings["foo"]}</p>
+${bindings["footer"]}"""