Optimize ScriptTemplatesFromDependenciesProvider

No needs to convert file.url to VirtualFile
because index already has getContainingFiles method
Do not iterate through all children of VirtualFile
to avoid VFS events initialisation for those files
there is no guarantee that file is under source root
so is can be not present is vfs at this moment

idea/scripting-support/testData/script/templatesFromDependencies/inJar/module/script.kts

@@ -0,0 +1 @@
+// needed for module creation

idea/scripting-support/testData/script/templatesFromDependencies/inJar/test.kts

@@ -0,0 +1,8 @@
+// ROOT: /templates.jar!/META-INF/kotlin/script/templates/MyTemplate1.classname
+// ROOT: /templates.jar!/inner/META-INF/kotlin/script/templates/MyTemplate2.classname
+
+// NAME: MyTemplate1
+// CLASSPATH: /templates.jar
+
+
+

idea/scripting-support/testData/script/templatesFromDependencies/inTests/test.kts

@@ -0,0 +1 @@
+// ROOT: /module/test/META-INF/kotlin/script/templates/MyTemplate.classname

idea/scripting-support/testData/script/templatesFromDependencies/multipleRoots/test.kts

@@ -0,0 +1,5 @@
+// ROOT: /module/resources/META-INF/kotlin/script/templates/MyTemplate1.classname
+// ROOT: /module/src/foo/META-INF/kotlin/script/templates/MyTemplate2.classname
+
+
+// NAME: MyTemplate1

idea/scripting-support/testData/script/templatesFromDependencies/multipleTemplates/test.kts

@@ -0,0 +1,5 @@
+// ROOT: /module/resources/META-INF/kotlin/script/templates/MyTemplate1.classname
+// ROOT: /module/resources/META-INF/kotlin/script/templates/MyTemplate2.classname
+
+// NAME: MyTemplate1
+// NAME: MyTemplate2

idea/scripting-support/testData/script/templatesFromDependencies/outsideRoots/test.kts

@@ -0,0 +1 @@
+

idea/scripting-support/testData/script/templatesFromDependencies/singleTemplate/test.kts

@@ -0,0 +1,4 @@
+// ROOT: /module/resources/META-INF/kotlin/script/templates/MyTemplate.classname
+
+// NAME: MyTemplate
+