pyoxidizer: support producing MSI installers Newer versions of PyOxidizer have support for building WiX MSI installers "natively." Essentially, you can script the definition of your WiX installer via Starlark and PyOxidizer can invoke WiX tools to produce the installer. This commit teaches our PyOxidizer config file to produce MSI installers similarly to how `contrib/packaging/packging.py wix` would do it. We had to make a very minor change to `mercurial.wxs` to reflect different paths depending on who builds. This is because when PyOxidizer builds WiX installers, it does so from an isolated directory, not Mercurial's source directory. We simply copy the files into the build environment so they are accessible. After this change, running `pyoxidizer build msi` produces a nearly identical install layout to what the previous method produces. When I applied this series on top of the 5.8 tag, here is the list of differences and explanations: * docs/*.html files are missing from the new installer because the Python build environment doesn't have docutils. * .pyd and .exe files differ, likely because I'm using a different Visual Studio toolchain on my local computer than the official build environment. * Various .dist-info/ directories have different names. This is because older versions of PyOxidizer had buggy behavior and weren't properly normalizing package names in .dist-info/ directories. e.g. we went from `cached-property-1.5.2.dist-info` to `cached_property-1.5.2.dist-info`. * Translations (.mo files) may be missing if gettext isn't in %Path%. This is because the packaging.py code installs gettext and ensures it can be found. * Some *.dist-info/RECORD files vary due to SHA-256 content digest divergence due to build environment differences. (This should be harmless.) * The new install layout ships a python3.dll because newer versions of PyOxidizer ship this file. * The new install layout has a different vcruntime140.dll and also a vcruntime140_1.dll because newer versions of PyOxidizer ship a newer version of the Visual C++ Redistributable Runtime. The new PyOxidizer functionality is not yet integrated with packaging.py. This will come in a subsequent commit. So for now, the new functionality introduced here is unused. Differential Revision: https://phab.mercurial-scm.org/D10683

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

pyoxidizer: remove some boilerplate in file This isn't used for anything and can safely be removed. Differential Revision: https://phab.mercurial-scm.org/D10678

contrib: upgrade Rust in Windows automation I'm not sure why we don't install the minimum required Rust version here like we do for Linux. Whatever: that's unrelated to wanting to stay modern. Differential Revision: https://phab.mercurial-scm.org/D10677

contrib: update Python versions in Windows automation Let's keep our Python versions modern. Differential Revision: https://phab.mercurial-scm.org/D10676

automation: update rust in Linux environment Our minimum supported Rust is 1.41.1 per rust/README.rst. We also bump the modern Rust version to latest stable to stay current. Differential Revision: https://phab.mercurial-scm.org/D10675

automation: install latest Python versions in Linux environment Let's keep our Linux environment up to date. Differential Revision: https://phab.mercurial-scm.org/D10674