Add granular pats decorator for runner REST endpoints

What does this MR do and why?

Make following endpoints granular PATs compliant

GET /api/v4/projects/:id/runners
POST /api/v4/projects/:id/runners
DELETE /api/v4/projects/:id/runners/:runner_id
POST /api/v4/projects/:id/runners/reset_registration_token

GET /api/v4/groups/:id/runners
POST /api/v4/groups/:id/runners/reset_registration_token

References

#575286

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. In Rails console, create a granular PAT for a user and copy a URL to create an issue with the token:

# Enable feature flag
Feature.enable(:authorize_granular_pats)

user = User.first

# Create granular token
token = PersonalAccessTokens::CreateService.new(
  current_user: user,
  target_user: user,
  organization_id: user.organization_id,
  params: { expires_at: 1.month.from_now, scopes: ['granular'], granular: true, name: 'gPAT' }
).execute[:personal_access_token]

# Get a project
project = user.projects.first

project_scope = Authz::GranularScope.new(namespace: project.project_namespace, permissions: [:read_runner])

Authz::GranularScopeService.new(token).add_granular_scopes(project_scope)

# Copy project avatar URL
IO.popen('pbcopy', 'w') { |f| f.puts "curl http://#{Gitlab.host_with_port}/api/v4/projects/#{project.id}/runners -X GET -H \"PRIVATE-TOKEN: #{token.token}\"" }

2. Paste the URL in another terminal. It should succeed.

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Related to #575286