Add a runtime agnostic enclave memory manager implementation in sdk/emm.
The EMM APIs are based on design proposed in this PR: https://github.com/openenclave/openenclave/pull/3991
Enclave common loader changes are in psw/enclave_common/sgx_mm_ocalls.cpp, which are basically
OCall support needed for EMM.
Intel SDK runtime specific support are implemented as runtime abstraction layer: sdk/trts/ema_rt.c
Current limitations, steps to build and test are documented in sdk/emm/README.md
Signed-off-by: Haitao Huang <4699115+haitaohuang@users.noreply.github.com>
Signed-off-by: Xiaofeng Xu <20158212+xxu36@users.noreply.github.com>