xds/third_party: fixed compatibility issue of regex in BSD for import.sh sed command (#5613)
xds/third_party: fixed compatibility issue of regex in BSD for import.sh sed command (#5613)

* fixed issue import.sh sed expr with non-extended regex does not support \| in BSD

* fixed sed -i issue for cross platform

ejona86/grpc-java,ejona86/grpc-java,dapengzhang0/grpc-java,stanley-cheung/grpc-java,ejona86/grpc-java,stanley-cheung/grpc-java,grpc/grpc-java,grpc/grpc-java,dapengzhang0/grpc-java,carl-mastrangelo/grpc-java,carl-mastrangelo/grpc-java,carl-mastrangelo/grpc-java,carl-mastrangelo/grpc-java,stanley-cheung/grpc-java,grpc/grpc-java,dapengzhang0/grpc-java,ejona86/grpc-java,stanley-cheung/grpc-java,grpc/grpc-java,dapengzhang0/grpc-java