Fix inner class name table emission with semantic names

The backend contains:

val outerName = innerClassSym.rawowner.javaBinaryName
// Java compatibility. See the big comment in BTypes that summarizes the InnerClass spec.
val outerNameModule = if (innerClassSym.rawowner.isTopLevelModuleClass) outerName.dropModule

Where `dropModule` is defined in the backend interface as:

def dropModule: Name = n.stripModuleClassSuffix

This will only work as expected if `javaBinaryName` returns a name with
proper semantic information, but before this commit we just used the
output of `fullNameSeparated` which contains no semantic information.

Author: smarter

compiler/src/dotty/tools/backend/jvm/DottyBackendInterface.scala

@@ -557,7 +557,8 @@ class DottyBackendInterface(outputDirectory: AbstractFile, val superCallsMap: Ma
     def fullName: String = sym.showFullName
     def simpleName: Name = sym.name
     def javaSimpleName: Name = toDenot(sym).name // addModuleSuffix(simpleName.dropLocal)
-    def javaBinaryName: Name = toDenot(sym).fullNameSeparated("/") // addModuleSuffix(fullNameInternal('/'))
+    def javaBinaryName: Name = toDenot(sym).fullNameSeparated("/").unmangleClassName // addModuleSuffix(fullNameInternal('/'))
+      // We use `unmangleClassName` so that `stripModuleClassSuffix` works as expected.
     def javaClassName: String = toDenot(sym).fullName.toString// addModuleSuffix(fullNameInternal('.')).toString
     def name: Name = sym.name
     def rawname: Name = {