build: use APT preferences to force SGX PSW and DCAP versions to what Occlum prefers

[mythi]

something like (but with an ARG override option) :

+++ b/tools/packaging/build/agent-enclave-bundle/Dockerfile
@@ -13,6 +13,7 @@ RUN apt-get update && \
 RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
 RUN echo "deb [arch=amd64 signed-by=/usr/share/keyrings/intel-sgx.gpg] https://download.01.org/intel-sgx/sgx_repo/ubuntu focal main" | tee -a /etc/apt/sources.list.d/intel-sgx.list \
  && wget -qO - https://download.01.org/intel-sgx/sgx_repo/ubuntu/intel-sgx-deb.key | gpg --dearmor --output /usr/share/keyrings/intel-sgx.gpg \
+ && wget -qO /etc/apt/preferences https://download.01.org/intel-sgx/sgx_repo/ubuntu/apt_preference_files/99sgx_2_17_100_focal_custom_version.cfg \
  && apt-get update \
  && env DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
     libsgx-dcap-ql \
@@ -44,7 +45,7 @@ RUN env DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommend
     occlum