[03693381] After the 7.6.6 upgrade, RH SSO is now consuming 100% of the CPU when using x509 authentication

See SSOSUP-686 and https://github.com/keycloak/keycloak/issues/26588 .

This issue is about:

• Investigate this issue and possibly reproduce with the certificate attached by customer
• Fix this in latest Keycloak main if reproducible (Corresponding GH issue is https://github.com/keycloak/keycloak/issues/26588). It can be OK to test this just with the unit tests in the "Crypto" module if we can reproduce with the unit test by customer and if customer is ok with sharing his certificate attached to SSOSUP-686 .
• Backport to RHSSO 7.6 (if issue is reproducible)