Less use of wxArrayString::Index() ...

... instead use the utility make_iterator_range and its index() or contains()
method.  This generic utility works with any container defining begin() and
end().

This further lessens dependency on wxWidgets container idioms.

src/commands/CommandManager.cpp

@@ -1603,7 +1603,7 @@ void CommandManager::GetCategories(wxArrayString &cats)
 
    for (const auto &entry : mCommandList) {
       wxString cat = entry->labelTop;
-      if (cats.Index(cat) == wxNOT_FOUND) {
+      if ( ! make_iterator_range( cats ).contains(cat) ) {
          cats.push_back(cat);
       }
    }

src/commands/LoadCommands.cpp

@@ -277,7 +277,7 @@ bool BuiltinCommandsModule::IsPluginValid(const wxString & path, bool bFast)
 {
    // bFast is unused as checking in the list is fast.
    static_cast<void>(bFast); // avoid unused variable warning
-   return mNames.Index(path) != wxNOT_FOUND;
+   return make_iterator_range( mNames ).contains( path );
 }
 
 ComponentInterface *BuiltinCommandsModule::CreateInstance(const wxString & path)
@@ -302,9 +302,10 @@ void BuiltinCommandsModule::DeleteInstance(ComponentInterface *instance)
 std::unique_ptr<AudacityCommand> BuiltinCommandsModule::Instantiate(const wxString & path)
 {
    wxASSERT(path.StartsWith(BUILTIN_GENERIC_COMMAND_PREFIX));
-   wxASSERT(mNames.Index(path) != wxNOT_FOUND);
+   auto index = make_iterator_range( mNames ).index( path );
+   wxASSERT( index != wxNOT_FOUND );
 
-   switch (mNames.Index(path))
+   switch ( index )
    {
       COMMAND_LIST;
       EXCLUDE_LIST;

src/commands/Validators.h

@@ -107,7 +107,7 @@ public:
    bool Validate(const wxVariant &v) override
    {
       SetConverted(v);
-      return (mOptions.Index(v.GetString()) != wxNOT_FOUND);
+      return make_iterator_range( mOptions ).contains( v.GetString() );
    }
    wxString GetDescription() const override
    {