pyoxidizer: use allocator_backend instead of raw_allocator The name of this attribute changed in PyOxidizer 0.11. Differential Revision: https://phab.mercurial-scm.org/D10682

pyoxidizer: simplify targets The split targets existed to enable the use of a non-default distribution flavor on Windows. Modern versions of PyOxidizer use the "standalone_dynamic" distribution flavor by default. So our split brain workaround is no longer needed. Here, we unify the targets. We also remove an unreferenced target function to create a resources file. Differential Revision: https://phab.mercurial-scm.org/D10681

contrib: install PyOxidizer 0.16.0 PyOxidizer now provides MSI installers and pre-built Linux binaries. So we install that way. This significantly reduces the time to bootstrap a new machine in automation, as building PyOxidizer from source on a low core count machine takes several minutes. This change temporarily breaks the ability of the automated environment to use the in-repo pyoxidizer.bzl configuration file, as there are backwards-incompatible changes with the upgrade that need to be reflected. We'll handle those in subsequent commits. Differential Revision: https://phab.mercurial-scm.org/D10680

pyoxidizer: pin Python to 3.8 Newer versions of PyOxidizer use version 3.9 by default. As part of upgrading PyOxidizer, we want to pin the version at 3.8 so we can compare differences more easily. Differential Revision: https://phab.mercurial-scm.org/D10679