Add support for Windows Server Core 2019 and friends.

- windows/servercore:ltsc2019
- windows/nanoserver:1809

…space

The GHA job output already croaked about this, like:

    You are running out of disk space. The runner will stop working when
    the machine runs out of disk space. Free space left: 0 MB

- windows/servercore:ltsc2016
- windows/servercore:ltsc2022
- windows/nanoserver:ltsc2022

- Don't manipulate $PATH. To make `git` available on the program search
  path, use the package parameter `/GitAndUnixToolsOnPath` instead.
- Rename native Windows programs like `curl.exe` and `convert.exe` to
  reduce ambiguity with their FOSS/GNU resp. Chocolatey-installed
  counterparts, also without needing to manipulate $PATH.
- Also install `busybox` and `nano`.

The new names are ``RACKER_WDM_VCPUS``, ``RACKER_WDM_MEMORY``, and
``RACKER_WDM_MACHINE``.

WDM means "Windows Docker Machine".

The new default values are:

- RACKER_WDM_VCPUS: 4
- RACKER_WDM_MEMORY: 4096 MB

This can be used to reconfigure the Vagrant virtualization backend
differently than VirtualBox.

Possible values are, in alphabetical order, `hyperv`, `virtualbox`,
`qemu`, `vmware_fusion`, `vmware_workstation`. It has been tested with
`virtualbox` only.

This aims to build Python wheels for PyTables in a DIY manner.

It uses Microsoft Visual C++ Build Tools 2015 and Anaconda, both
installed using Chocolatey, and `cibuildwheel`.