Eliminate last use of PluginManager by ModuleManager, breaking cycle

src/ModuleManager.cpp

@@ -31,7 +31,6 @@ i.e. an alternative to the usual interface, for Audacity.
 
 #include "FileNames.h"
 #include "MemoryX.h"
-#include "PluginManager.h"
 
 #include "audacity/PluginInterface.h"
 
@@ -488,22 +487,6 @@ void ModuleInterfaceDeleter::operator() (ModuleInterface *pInterface) const
    }
 }
 
-PluginPaths ModuleManager::FindPluginsForProvider(const PluginID & providerID,
-                                                    const PluginPath & path)
-{
-   // Instantiate if it hasn't already been done
-   if (mDynModules.find(providerID) == mDynModules.end())
-   {
-      // If it couldn't be created, just give up and return an empty list
-      if (!CreateProviderInstance(providerID, path))
-      {
-         return {};
-      }
-   }
-
-   return mDynModules[providerID]->FindPluginPaths(PluginManager::Get());
-}
-
 bool ModuleManager::RegisterEffectPlugin(const PluginID & providerID, const PluginPath & path, TranslatableString &errMsg)
 {
    errMsg = {};

src/ModuleManager.h

@@ -103,7 +103,6 @@ public:
    auto Providers() const
    { return make_iterator_range(mDynModules.cbegin(), mDynModules.cend()); }
 
-   PluginPaths FindPluginsForProvider(const PluginID & provider, const PluginPath & path);
    bool RegisterEffectPlugin(const PluginID & provider, const PluginPath & path,
                        TranslatableString &errMsg);
 

src/PluginManager.cpp

@@ -1382,7 +1382,9 @@ void PluginManager::CheckForUpdates(bool bFast)
          else
          {
             // Collect plugin paths
-            auto paths = mm.FindPluginsForProvider(plugID, plugPath);
+            PluginPaths paths;
+            if (auto provider = mm.CreateProviderInstance( plugID, plugPath ) )
+               paths = provider->FindPluginPaths( *this );
             for (size_t i = 0, cnt = paths.size(); i < cnt; i++)
             {
                wxString path = paths[i].BeforeFirst(wxT(';'));;