Fix nagivation from Global Settings --> Performance to any Cluster Ex…

…plorer custom list

- 2.8 based bug
- Only reproducible when
  - performance settings have been changed
  - navigating from performance page to list page
- Root effect
  - Contstant trigger of two computed properties
     - namespaceFilterRequired
       - shell/mixins/resource-fetch-namespaced.js
     - namespaceFilter --> __namespaceRequired --> value (all same colour, suggesting our code)
       - tracing shows this also to start from shell/mixins/resource-fetch-namespaced.js

shell/pages/c/_cluster/settings/performance.vue

@@ -61,7 +61,7 @@ export default {
 
   data() {
     return {
-      uiPerfSetting:              DEFAULT_PERF_SETTING,
+      uiPerfSetting:              null,
       authUserTTL:                null,
       bannerVal:                  {},
       value:                      {},

shell/utils/settings.ts

@@ -102,5 +102,7 @@ export const getPerformanceSetting = (rootGetters: Record<string, (arg0: string,
   }
 
   // Start with the default and overwrite the values from the setting - ensures we have defaults for newly added options
-  return Object.assign(DEFAULT_PERF_SETTING, perfSetting || {});
+  const safeDefaults = Object.assign({}, DEFAULT_PERF_SETTING);
+
+  return Object.assign(safeDefaults, perfSetting || {});
 };