Fix findReferences for modules

For modules we sometimes get the module class instead of the module
val as symbol. In that case we should not filter references by the module class
name but by the module name.

Author: odersky

language-server/src/dotty/tools/languageserver/DottyLanguageServer.scala

@@ -243,7 +243,7 @@ class DottyLanguageServer extends LanguageServer
       // FIXME: this will search for references in all trees on the classpath, but we really
       // only need to look for trees in the target directory if the symbol is defined in the
       // current project
-      val trees = driver.allTreesContaining(sym.name.toString)
+      val trees = driver.allTreesContaining(sym.name.sourceModuleName.toString)
       val refs = Interactive.namedTrees(trees, includeReferences = true, (tree: tpd.NameTree) =>
         (includeDeclaration || !Interactive.isDefinition(tree))
           && Interactive.matchSymbol(tree, sym, includeOverridden = true))
@@ -262,7 +262,7 @@ class DottyLanguageServer extends LanguageServer
 
     if (sym == NoSymbol) new WorkspaceEdit()
     else {
-      val trees = driver.allTreesContaining(sym.name.toString)
+      val trees = driver.allTreesContaining(sym.name.sourceModuleName.toString)
       val linkedSym = sym.linkedClass
       val newName = params.getNewName