Remove a bunch of old/unused xtask things #39

Job	Run time
build_attest_all (buildconfigs/key_xor_test_app.sh)	3s
build_attest_all (buildconfigs/oak_containers_kernel.sh)	3s
build_attest_all (buildconfigs/oak_containers_orchestrator.sh)	4s
build_attest_all (buildconfigs/oak_containers_stage1.sh)	3s
build_attest_all (buildconfigs/oak_containers_syslogd.sh)	4s
build_attest_all (buildconfigs/oak_containers_system_image.sh)	7s
build_attest_all (buildconfigs/oak_echo_enclave_app.sh)	5s
build_attest_all (buildconfigs/oak_echo_raw_enclave_app.sh)	7s
build_attest_all (buildconfigs/oak_functions_enclave_app.sh)	6s
build_attest_all (buildconfigs/oak_functions_insecure_enclave_app.sh)	4s
build_attest_all (buildconfigs/oak_restricted_kernel_simple_io_init_rd_wrapper_bin.sh)	5s
build_attest_all (buildconfigs/stage0_bin.sh)	3s
build_attest_all (buildconfigs/oak_orchestrator.sh)	5s
	59s

Provide feedback