Metrics: Usage ping for project templates

Description

There is no way to track if users are leveraging project templates to start their applications. To understand the adoption of this feature, we should add template data to usage ping.

Proposal

Add project template information to usage ping (example usage ping addition MR):

• Newly created number of projects created from a template
• Users creating projects
• Total number of projects on the instance that were created from templates
• Specific counters for each template used

Pseudocode example

Let's say that a self-managed instance has 300 projects and 20 of them were created from templates. 3 users create 10 more projects, all from the Rails template, next month. The JSON sent in usage ping may contain a blob looking something like:

"new_projects_created_from_template": "10",
"users_creating_projects_from_template": "3",
"total_projects_created_from template": {
  "total": "30",
  "built-in": {
    "rails": "10",
    "spring": "0",
    ...
    }
  "custom": {
    "foo": "0",
    ...
    }
  }