Add staging deployment of the runner on dev branches

• Switch to using terraform base template
• Drop unused variables
• Do not allow failure on terraform fmt jobs
• Add overridable services_instance_count defaulting to 1
• Use general project variables for all operations
• Add runner_flavor config variable
• Add environment name to runner name
• Add staging deployment of the runner on dev branches
• Mark jobs as interruptible by default
• Only run merge request and master pipelines
• Add trivial example project to repo
• Add basic test stage
• Only run before_script for select jobs