Switch to C++20

PiperOrigin-RevId: 573677424

.bazelrc

@@ -1,10 +1,10 @@
 build --client_env=CC=clang
 
-build --cxxopt=-std=c++17 --cxxopt=-fno-stack-protector --copt=-Wno-narrowing --copt=-fno-exceptions --cxxopt=-Wno-unused-private-field --cxxopt=-Wno-defaulted-function-deleted
+build --cxxopt=-std=c++20 --cxxopt=-fno-stack-protector --copt=-Wno-narrowing --copt=-fno-exceptions --cxxopt=-Wno-unused-private-field --cxxopt=-Wno-defaulted-function-deleted
 
 # SiliFuzz build is "selfhosted" (i.e. uses its own stack for some of the build tools).
 # Use the same configuration as the target above
-build --host_cxxopt=-std=c++17 --host_cxxopt=-fno-stack-protector --host_copt=-Wno-narrowing --host_copt=-fno-exceptions --host_cxxopt=-Wno-unused-private-field --host_cxxopt=-Wno-defaulted-function-deleted
+build --host_cxxopt=-std=c++20 --host_cxxopt=-fno-stack-protector --host_copt=-Wno-narrowing --host_copt=-fno-exceptions --host_cxxopt=-Wno-unused-private-field --host_cxxopt=-Wno-defaulted-function-deleted
 
 # Remove security hardening as it clashes with nolibc
 build --copt -U_FORTIFY_SOURCE