Instrumentation: include view template path in render.view_component payload

[Copilot]

The render.view_component event payload only included the component's .rb identifier, making it impossible for tools like Coverband to track which view templates are actually rendered.

Changes

• lib/view_component/instrumentation.rb: Adds view_identifier to the event payload — the path to the rendered template file (e.g. my_component.html.erb). Uses an around_render override to capture current_template.path at the right moment: after rendering sets @current_template but before Base#render_in's ensure block restores it. view_identifier is nil for components using inline call methods (no template file).
• test/sandbox/test/instrumentation_test.rb: Asserts view_identifier is present and correct in the event payload.
• docs/guide/instrumentation.md: Updated example payload to reflect new field.

Updated payload

ActiveSupport::Notifications.subscribe("render.view_component") do |event|
  event.payload
  # => {
  #   name: "MyComponent",
  #   identifier: "/app/components/my_component.rb",
  #   view_identifier: "/app/components/my_component.html.erb"  # nil for inline call components
  # }
end

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