fa5a02bcfa ci: Use clang-20 for sanitizer tasks (MarcoFalke)
Pull request description:
A new clang version generally comes with bugfixes, new (sanitizer) features, and deprecations.
Upgrade the sanitizer tasks to use the new version.
This was also suggested in https://github.com/bitcoin/bitcoin/pull/31691#issuecomment-2602517116
ACKs for top commit:
fanquake:
ACK fa5a02bcfa - tested 20 in some other infra, we just needed to fix the same deprecation warnings we'd seen, in cryptofuzz: 09ca550c3e.
Tree-SHA512: 6114d790b5d7145eb5f019e02da6c2c833342707ad67fb9f9c09506001afbef0c9b9beee7e51321f17f12ea692509d6428e6072ad105dba51e4d54cd057621cd
