Ninja Multi-Config: Restore rebuild_cache and edit_cache targets

Since commit dcf9f4d2f7 (Ninja Multi-Config: Add support for
cross-config custom commands, 2020-12-09) we were not generating these
targets.  Restore them and add a test.

Fixes: #21722

Source/cmNinjaUtilityTargetGenerator.cxx

@@ -35,6 +35,11 @@ cmNinjaUtilityTargetGenerator::~cmNinjaUtilityTargetGenerator() = default;
 
 void cmNinjaUtilityTargetGenerator::Generate(const std::string& config)
 {
+  if (!this->GetGeneratorTarget()->Target->IsPerConfig()) {
+    this->WriteUtilBuildStatements(config, config);
+    return;
+  }
+
   for (auto const& fileConfig : this->GetConfigNames()) {
     if (!this->GetGlobalGenerator()
            ->GetCrossConfigs(fileConfig)