[jvm-lang] refactor & cleanup action utils

- add and use JvmSubstitutor.toPsiSubstitutor();
- rename JvmModifier.toPsi to toPsiModifier, make it internal;
- make toJavaClassOrNull() internal.

java/java-impl/src/com/intellij/lang/java/actions/CreateFieldAction.kt

@@ -140,10 +140,10 @@ private fun extractRenderData(targetClass: PsiClass, request: CreateFieldRequest
     targetClass,
     fieldName,
     extractExpectedTypes(project, request.fieldType).toTypedArray(),
-    JvmPsiConversionHelper.getInstance(project).convertSubstitutor(request.targetSubstitutor),
+    request.targetSubstitutor.toPsiSubstitutor(project),
     javaUsage?.reference,
     javaUsage?.anchor,
-    modifiersToRender.map(JvmModifier::toPsi),
+    modifiersToRender.map(JvmModifier::toPsiModifier),
     renderConstant
   )
 }

java/java-impl/src/com/intellij/lang/java/actions/CreateMethodAction.kt

@@ -134,7 +134,7 @@ private class JavaMethodRenderer(
     }
 
     for (modifier in modifiersToRender) {
-      setModifierProperty(method, modifier.toPsi(), true)
+      setModifierProperty(method, modifier.toPsiModifier(), true)
     }
 
     for (annotation in request.annotations) {
@@ -159,7 +159,7 @@ private class JavaMethodRenderer(
 
   private fun setupTemplate(method: PsiMethod): TemplateBuilderImpl {
     val builder = TemplateBuilderImpl(method)
-    val substitutor = JvmPsiConversionHelper.getInstance(project).convertSubstitutor(request.targetSubstitutor)
+    val substitutor = request.targetSubstitutor.toPsiSubstitutor(project)
     val guesser = GuessTypeParameters(project, factory, builder, substitutor)
     setupTypeElement(guesser, method.returnTypeElement, request.returnType)
     builder.setupParameters(guesser, method)

java/java-impl/src/com/intellij/lang/java/actions/jvmPsiUtil.kt

@@ -24,16 +24,14 @@ import com.intellij.lang.jvm.JvmClass
 import com.intellij.lang.jvm.JvmModifier
 import com.intellij.lang.jvm.actions.ExpectedType
 import com.intellij.lang.jvm.actions.ExpectedTypes
+import com.intellij.lang.jvm.types.JvmSubstitutor
 import com.intellij.openapi.project.Project
-import com.intellij.psi.JvmPsiConversionHelper
-import com.intellij.psi.PsiClass
-import com.intellij.psi.PsiModifier
+import com.intellij.psi.*
 import com.intellij.psi.PsiModifier.ModifierConstant
-import com.intellij.psi.PsiTypeParameter
 import com.intellij.psi.impl.compiled.ClsClassImpl
 
 @ModifierConstant
-fun JvmModifier.toPsi(): String = when (this) {
+internal fun JvmModifier.toPsiModifier(): String = when (this) {
   JvmModifier.PUBLIC -> PsiModifier.PUBLIC
   JvmModifier.PROTECTED -> PsiModifier.PROTECTED
   JvmModifier.PRIVATE -> PsiModifier.PRIVATE
@@ -55,7 +53,7 @@ fun JvmModifier.toPsi(): String = when (this) {
  *
  * @return Java PsiClass or `null` if the receiver is not a Java PsiClass
  */
-fun JvmClass.toJavaClassOrNull(): PsiClass? {
+internal fun JvmClass.toJavaClassOrNull(): PsiClass? {
   if (this !is PsiClass) return null
   if (this is PsiTypeParameter) return null
   if (this is ClsClassImpl) return null
@@ -91,3 +89,7 @@ private fun ExpectedType.Kind.infoKind(): Int {
     ExpectedType.Kind.SUBTYPE -> ExpectedTypeInfo.TYPE_OR_SUBTYPE
   }
 }
+
+internal fun JvmSubstitutor.toPsiSubstitutor(project: Project): PsiSubstitutor {
+  return JvmPsiConversionHelper.getInstance(project).convertSubstitutor(this)
+}