Agents, Services and Nodes can now be removed via the 'PMM Inventory' page

The problem: there is no easy way to remove Services, Nodes, and Agents from the web UI. There are only some workarounds with pmm-admin

The Goal: Provide the ability to Delete objects (Nodes. Services, Agents)
Additionally, we need to let people use "force" mode

Use cases: 

1. As a PMM Admin User, I can remove one or several Agents from PMM so that they are no longer collecting data about Nodes or Services in the PMM
2. As a PMM Admin user, I need to be able to remove one or several Services from being monitored with the ability to use Force mode to remove all agent related to this service, so the Service is no longer monitored 

UI:

Example for Services: ** 

• * 

DOC: 

• Page, like https://www.percona.com/doc/percona-monitoring-and-management/2.x/manage/server-admin-gui.html to describe elements on the page  

Out of Scope:

• Big structure (Object relations and presentation ) Improvements in Inventory page
• API changes  out of scope 
• No Data purges  for this  task 

Note:

• in 1-2 releases we are planning to rework this page from UI  side very intensively 

Questions:

• Technical side if implementation - use Grafana components where possible?
  • migration to Grafana UI 
• does "force" mode make sense for Not Services? will it delete a node by default too? 
  • yes, no node will stay