E2E test: use testids for generate commit spec

What does this MR do and why?

In https://gitlab.com/gitlab-org/gitlab/-/issues/506323 we sawee/browser_ui/3_create/merge_request/generate_commit_message_spec.rb fail due to multiple elements having Insert in the name. This MR gives the button a data-testid so it can be uniquely identifed.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

This test runs against live environments only, but it can be verified against a GDK with Duo Enterprise:

0. GDK has Duo Enterprise
1. Add break point so seat can be assigned to test user:

diff --git a/qa/qa/specs/features/ee/browser_ui/3_create/merge_request/generate_commit_message_spec.rb b/qa/qa/specs/features/ee/browser_ui/3_create/merge_request/generate_commit_message_spec.rb
index 02c9280eb0d7..721b1694251b 100644
--- a/qa/qa/specs/features/ee/browser_ui/3_create/merge_request/generate_commit_message_spec.rb
+++ b/qa/qa/specs/features/ee/browser_ui/3_create/merge_request/generate_commit_message_spec.rb
@@ -20,6 +20,9 @@ module QA
           ])
 
         Flow::Login.sign_in
+        require 'pry'
+        binding.pry
+        # Add duo seat for test user https://gdk.test:3443/admin/gitlab_duo/seat_utilization and then resume test
         merge_request.visit!
       end
 

1. QA_LOG_LEVEL=DEBUG QA_GITLAB_URL=https://gdk.test:3443 GITLAB_QA_ADMIN_ACCESS_TOKEN=x bundle exec rspec qa/specs/features/ee/browser_ui/3_create/merge_request/generate_commit_message_spec.rb

gencommit