Envoy supports executing CEL expressions. We need an API of type

int32 expression_handle  compile_cel_expr(std::string expr);

wasmResult evaluate_cel_expr(handle);

Advantages:

1. This way the entire expression is evaluated inside the host. CEL offers safety. Since CEL executes in the host, it will not incur multiple back roundtrips across the VM
2. Expressions can be moved to config, instead of C++ code. This means that when expression changes, we do not need to recompile and deploy WASM code. This saves on transport and v8 cache costs.