Add dashboard statistics module and refactor views for metrics handling

- Introduced a new `stats.py` module to encapsulate dashboard statistics building and cache key constants.
- Refactored `views.py` to utilize the new `build_stats` function for constructing metrics context, improving code organization and readability.
- Updated Prometheus query handling to streamline metrics fetching with a new `fetch_dashboard_metrics` function.
- Enhanced test cases to reflect changes in metrics fetching and context building, ensuring accurate functionality.
- Added new HTML templates for displaying detailed resource allocation and flavor statistics on the dashboard.

watcher_visio/settings.py

@@ -48,7 +48,7 @@ INSTALLED_APPS = [
 PROMETHEUS_URL = "http://10.226.74.53:9090/"
 PROMETHEUS_METRICS = {
     "cpu_usage": "rate(libvirt_domain_info_cpu_time_seconds_total)[300s]",
-    "ram_usage": "avg_over_time(libvirt_domain_info_memory_usage_bytes[300s]",
+    "ram_usage": "avg_over_time(libvirt_domain_info_memory_usage_bytes[300s])",
 }
 
 # Openstack cloud settings