devenv: update ha test and load test

better ha setup for many mysql connections
prometheus now scrapes mysql metrics in ha setup
ha setup provisions mysql dashboard
adds configurable virtual users for load test run script

devenv/docker/ha_test/prometheus/prometheus.yml

@@ -30,10 +30,10 @@ scrape_configs:
         port: 3000
         refresh_interval: 10s
 
-  # - job_name: 'mysql'
-  #   dns_sd_configs:
-  #     - names:
-  #       - 'mysqld-exporter'
-  #       type: 'A'
-  #       port: 9104
-  #       refresh_interval: 10s
+  - job_name: 'mysql'
+    dns_sd_configs:
+      - names:
+        - 'mysqld-exporter'
+        type: 'A'
+        port: 9104
+        refresh_interval: 10s