fix(windows): base layout support in Keyman Core

While Keyman Core already supported the base layout flags, they were not
being passed in from Keyman Engine for Windows. This meant that any
rules that used `baselayout` would fail, such as in sil_ipa with AltGr+0
for }

https://github.com/keymanapp/keyboards/blob/0bf72bed74f563f823b1af002f6a8ccef8510ebf/release/sil/sil_ipa/source/sil_ipa.kmn#L348-L350

This patch adds support for the following properties:

* KM_KBP_KMX_ENV_BASELAYOUT: the legacy base layout name, e.g. kbdus.dll
* KM_KBP_KMX_ENV_BASELAYOUTALT: the BCP 47 base layout name, e.g. en-US
* KM_KBP_KMX_ENV_SIMULATEALTGR: whether the user has selected to emulate
  AltGr with Ctrl+Alt, for example on laptops without a right alt key.
* KM_KBP_KMX_ENV_BASELAYOUTGIVESCTRLRALTFORRALT: whether the system base
  layout in use generates Ctrl+RAlt when RAlt is pressed, which can be
  true for many European system layouts. This is necessary when
  associating the keyboard with a European language because the base
  keyboard becomes the language's default keyboard, rather than kbdus.