feat(xds): rework DeltaXds to use metadata instead of proto #14794

Job	Run time
check	16m 22s
test / test_unit	18m 21s
test / gen_e2e_matrix	3s
test / test_e2e	0s
test / test_e2e_env (kubernetes, v1.32.2-k3s1, amd64, 1, flannel) / e2e (0)	23m 36s
test / test_e2e_env (multizone, v1.32.2-k3s1, amd64, 1, flannel) / e2e (0)	25m 49s
test / test_e2e_env (universal, kind, amd64, 1, flannel) / e2e (0)	16m 24s
distributions	6s
provenance	0s
build_publish	0s
	1h 40m 41s

Provide feedback