Simplify VirtualFileFinder and their factories' hierarchy

Since there's no JsVirtualFileFinder anymore, inline JvmVirtualFileFinder into
VirtualFileFinder and drop "Jvm" prefix everywhere

compiler/frontend/src/org/jetbrains/kotlin/load/kotlin/VirtualFileFinder.kt

@@ -1,24 +0,0 @@
-/*
- * Copyright 2010-2015 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.jetbrains.kotlin.load.kotlin
-
-import com.intellij.openapi.vfs.VirtualFile
-import org.jetbrains.kotlin.name.ClassId
-
-interface VirtualFileFinder {
-    fun findVirtualFileWithHeader(classId: ClassId): VirtualFile?
-}

compiler/frontend/src/org/jetbrains/kotlin/load/kotlin/VirtualFileFinderFactory.kt

@@ -1,23 +0,0 @@
-/*
- * Copyright 2010-2015 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package org.jetbrains.kotlin.load.kotlin
-
-import com.intellij.psi.search.GlobalSearchScope
-
-interface VirtualFileFinderFactory {
-    fun create(scope: GlobalSearchScope): VirtualFileFinder
-}