Move to C++ 20

Signed-off-by: Aditya Pande <[email protected]>

Author: adityapande-1995

default.bazelrc

@@ -1,6 +1,6 @@
-# Use C++17.
-build --cxxopt=-std=c++17
-build --host_cxxopt=-std=c++17
+# Use C++20.
+build --cxxopt=-std=c++20
+build --host_cxxopt=-std=c++20
 
 # Use Python 3.
 build --python_path=/usr/bin/python3