Merge bitcoin#30735: ci: Use C++23 in one task

fac587e ci: Use C++23 once for testing (MarcoFalke)
fa053ab build: Add Centos Stream 9 EOL URL (MarcoFalke)

Pull request description:

  There are no plans to switch to C++23 anytime soon in the next couple of years. The only place right now that is known to benefit is `src/compat/byteswap.h`.

  However, it is still useful to test with the option, because deprecated, removed or changed language features, as well as compiler changes that are guarded by the language version will be tested and developers can learn about them upfront.

  Also includes a minor doc fixup commit.

ACKs for top commit:
  davidgumberg:
    ACK bitcoin@fac587e
  TheCharlatan:
    ACK fac587e

Tree-SHA512: 1b81788eb5b4da77715d8b047279de65ae6b8920d5a21fd8cc94c3b0edb588ab8ffb7eaffb2f8b7806045de1d47ca85ca629f49038eca762f3136bf380cf3c87

CMakeLists.txt

@@ -5,7 +5,7 @@
 # Ubuntu 22.04 LTS Jammy Jellyfish, https://wiki.ubuntu.com/Releases, EOSS in June 2027:
 #  - CMake 3.22.1, https://packages.ubuntu.com/jammy/cmake
 #
-# Centos Stream 9, EOL in May 2027:
+# Centos Stream 9, https://www.centos.org/cl-vs-cs/#end-of-life, EOL in May 2027:
 #  - CMake 3.26.5, https://mirror.stream.centos.org/9-stream/AppStream/x86_64/os/Packages/
 cmake_minimum_required(VERSION 3.22)
 if(POLICY CMP0141)

ci/test/00_setup_env_native_asan.sh

@@ -28,7 +28,8 @@ export BITCOIN_CONFIG="\
  -DCMAKE_C_COMPILER=clang-18 \
  -DCMAKE_CXX_COMPILER=clang++-18 \
  -DCMAKE_C_FLAGS='-ftrivial-auto-var-init=pattern' \
- -DCMAKE_CXX_FLAGS='-ftrivial-auto-var-init=pattern' \
+ -DCMAKE_CXX_FLAGS='-ftrivial-auto-var-init=pattern -Wno-error=deprecated-declarations' \
+ -DAPPEND_CXXFLAGS='-std=c++23' \
  -DAPPEND_CPPFLAGS='-DARENA_DEBUG -DDEBUG_LOCKORDER' \
 "
 export CCACHE_MAXSIZE=300M