packaging: support building Inno installer with PyOxidizer We want to start distributing Mercurial on Python 3 on Windows. PyOxidizer will be our vehicle for achieving that. This commit implements basic support for producing Inno installers using PyOxidizer. While it is an eventual goal of PyOxidizer to produce installers, those features aren't yet implemented. So our strategy for producing Mercurial installers is similar to what we've been doing with py2exe: invoke a build system to produce files then stage those files into a directory so they can be turned into an installer. We had to make significant alterations to the pyoxidizer.bzl config file to get it to produce the files that we desire for a Windows install. This meant differentiating the build targets so we can target Windows specifically. We've added a new module to hgpackaging to deal with interacting with PyOxidizer. It is similar to pyexe: we invoke a build process then copy files to a staging directory. Ideally these extra files would be defined in pyoxidizer.bzl. But I don't think it is worth doing at this time, as PyOxidizer's config files are lacking some features to make this turnkey. The rest of the change is introducing a variant of the Inno installer code that invokes PyOxidizer instead of py2exe. Comparing the Python 2.7 based Inno installers with this one, the following changes were observed: * No lib/*.{pyd, dll} files * No Microsoft.VC90.CRT.manifest * No msvc{m,p,r}90.dll files * python27.dll replaced with python37.dll * Add vcruntime140.dll file The disappearance of the .pyd and .dll files is acceptable, as PyOxidizer has embedded these in hg.exe and loads them from memory. The disappearance of the *90* files is acceptable because those provide the Visual C++ 9 runtime, as required by Python 2.7. Similarly, the appearance of vcruntime140.dll is a requirement of Python 3.7. Differential Revision: https://phab.mercurial-scm.org/D8473