Pins all the build dependencies required by poetry, otherwise
poetry installs arbitrary versions of them, which leads to a wrong
version of cryptography being installed and the build failing.
Note that Cloud dependencies (pillar and the like) has to have their
build dependencies pinned in the same exact manner, for the same reason.
Pins all the runtime dependencies as well, because Cloud can only use
poetry==1.0 due to its source dependencies, so there's no
"poetry lock --no-update" and each "poetry lock" updates arbitrary packages.
