Add tests for send_file and redirect_to instrumentation

[p8]

It seems these weren't tested before.

Caching instrumentation is tested in a similar way:

rails/actionpack/test/controller/caching_test.rb

Lines 257 to 270 in a5f113f

	def test_fragment_cache_instrumentation
	payload = nil
	subscriber = proc do |_, _, _, _, event_payload|
	payload = event_payload
	end
	ActiveSupport::Notifications.subscribed(subscriber, "read_fragment.action_controller") do
	get :inline_fragment_cached
	end
	assert_equal "functional_caching", payload[:controller]
	assert_equal "inline_fragment_cached", payload[:action]
	end

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.

[bdewater]

It's minor but in #49433 I was hoping people would move away from this pattern ;)

[p8]

Bedankt @bdewater 😄 #49467