Pass byte pointers rather than PlaintextMessages #767

Job	Run time
build_attest_all (buildconfigs/key_xor_test_app.sh)	43m 41s
build_attest_all (buildconfigs/oak_client_android_app.sh)	50m 36s
build_attest_all (buildconfigs/oak_containers_agent.sh)	34m 30s
build_attest_all (buildconfigs/oak_containers_kernel.sh)	37m 4s
build_attest_all (buildconfigs/oak_containers_orchestrator.sh)	52m 29s
build_attest_all (buildconfigs/oak_containers_stage1.sh)	50m 38s
build_attest_all (buildconfigs/oak_containers_syslogd.sh)	48m 0s
build_attest_all (buildconfigs/oak_containers_system_image.sh)	51m 21s
build_attest_all (buildconfigs/oak_containers_nvidia_system_image.sh)	50m 56s
build_attest_all (buildconfigs/oak_echo_enclave_app.sh)	44m 34s
build_attest_all (buildconfigs/oak_echo_raw_enclave_app.sh)	44m 27s
build_attest_all (buildconfigs/oak_functions_enclave_app.sh)	41m 38s
build_attest_all (buildconfigs/oak_functions_insecure_enclave_app.sh)	43m 47s
build_attest_all (buildconfigs/oak_orchestrator.sh)	43m 37s
build_attest_all (buildconfigs/oak_restricted_kernel_simple_io_init_rd_wrapper_bin.sh)	44m 44s
build_attest_all (buildconfigs/stage0_bin.sh)	41m 42s
build_attest_all (buildconfigs/stage0_bin_tdx.sh)	43m 0s
	12h 46m 44s

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