chore(storage): fix test failures for universe domain and requester pays

[aandreassa]

Nightly acceptance crashed the google-cloud-storage suite due to missing secrets (failing to load).

This unblocks CI by:

1. Adding universe domain secrets to nightly/continuous Kokoro configs, matching presubmit.
2. Rescuing missing secret errors in universe_domain_test.rb to log and skip instead of crashing.

Follow-up PRs will address individual failing tests once nightly runs again. Bug: 552162906

Example Logs:

[acceptance/storage/universe_domain_test.rb:20](https://cs.corp.google.com/piper///depot/google3/acceptance/storage/universe_domain_test.rb?l=20):in 'File.realpath': No such file or directory @ rb_check_realpath_internal - /secrets/gfile/secret_manager/client-library-test-universe-project-id (Errno::ENOENT)
	from [acceptance/storage/universe_domain_test.rb:20](https://cs.corp.google.com/piper///depot/google3/acceptance/storage/universe_domain_test.rb?l=20):in 'block in <top (required)>'
	from /[h/.gem/gems/minitest-5.27.0/lib/minitest/spec.rb:99](https://cs.corp.google.com/piper///depot/google3/h/.gem/gems/minitest-5.27.0/lib/minitest/spec.rb?l=99):in 'Module#class_eval'
	from /[h/.gem/gems/minitest-5.27.0/lib/minitest/spec.rb:99](https://cs.corp.google.com/piper///depot/google3/h/.gem/gems/minitest-5.27.0/lib/minitest/spec.rb?l=99):in 'Kernel#describe'
	from [acceptance/storage/universe_domain_test.rb:17](https://cs.corp.google.com/piper///depot/google3/acceptance/storage/universe_domain_test.rb?l=17):in '<top (required)>'
	from /[tmp/toys-minitest-script-20260828-4032-vsb1ak.rb:28](https://cs.corp.google.com/piper///depot/google3/tmp/toys-minitest-script-20260828-4032-vsb1ak.rb?l=28):in 'Kernel#load'
	from /[tmp/toys-minitest-script-20260828-4032-vsb1ak.rb:28](https://cs.corp.google.com/piper///depot/google3/tmp/toys-minitest-script-20260828-4032-vsb1ak.rb?l=28):in '<main>'
[2026-08-28 08:04:03 ERROR]  Minitest failed!