test: cover anonymous security alternatives

[kriptoburak]

Summary

• Add a ruleset regression test for operation security lists that include an anonymous alternative.
• Keep the existing scheme usage valid while covering the empty security requirement object from OpenAPI.

Validation

• git diff --check
• node --check packages/ruleset/test/rules/securityschemes.test.js
• Not run: npm ci or npm run test-ruleset because this clone has no node_modules and local disk is nearly full.

[CLAassistant]

All committers have signed the CLA.

[pyrooka]

Hi @kriptoburak, thanks for your contribution. Looks like you haven't accepted the CLA yet, so please do that. Also, the tests fail so we need to fix them. Would you mind adjusting the rule to handle empty/anonym security schemes correctly?