[#2818] - Skip simulateFailedLogin for AllowAllCredentialsMatcher

[arimu1]

Summary

Fixes #2818.

AllowAllCredentialsMatcher always returns true from doCredentialsMatch, so it cannot provide decoy simulated credentials that fail matching. When a multi-realm setup asks such a realm about an unknown principal, simulateFailedLogin was treating the decoy as a misconfiguration and logging a false IncorrectCredentialsException error on every login.

This change:

• Returns Optional.empty() from AllowAllCredentialsMatcher#createSimulatedCredentials()
• Caches the opt-out in AuthenticatingRealm#ensureSimulatedAuthenticationInfo so empty simulated credentials are not re-requested on every lookup
• Skips the misconfiguration warning for AllowAllCredentialsMatcher, since opting out is intentional

Test plan

• mvn -pl core -am test -Dtest=AllowAllCredentialsMatcherTest,AuthenticatingRealmJavaTest -Dsurefire.failIfNoSpecifiedTests=false (JDK 21)
• Added regression test for unknown principal + AllowAllCredentialsMatcher
• Added test asserting createSimulatedCredentials() is empty

Made with LLM

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[lprimak]

Can you please restore the PR template. PRs cannot be accepted without it, and copyright / license attribution

[lprimak]

Please check the appropriate box in the description checklist to attribute license and copyright to Apache.

Thank you for your contribution.

[lprimak]

I have reviewed your PR. I think it's way over-complicated. It inspired me to write much simpler PR.
Once again, thank you for your contribution as it inspired me. I will close this PR in favor of #2856