refactor(windows): merge keyman64 build into keyman32

[mcdurdin]

Merges the build settings for keyman64.dll vc++ project into the keyman32.dll project, so they are both built from the same project, in preparation for ARM support, to minimize repetition in the source tree.

There should be no material differences to the built libraries.

Also cleans up some noise in keyman32.vcxproj which made it easier to verify the changes.

Fixes: #11904

User Testing

• TEST_WINDOWS: Please run a basic test of Windows functionality, verifying that Keyman operates as expected.

[keymanapp-test-bot[bot]]

User Test Results

Test specification and instructions

• ✅ TEST_WINDOWS (PASSED): I tested this issue with the attached "keyman-18.0.66.exe" build on the Windows 10 and 11 OS environments: Here is my observation. (notes)

[dinakaranr]

Test Results

• TEST_WINDOWS (Passed): I tested this issue with the attached "keyman-18.0.66.exe" build on the Windows 10 and 11 OS environments: Here is my observation.

1. Installed the "keyman-18.0.66.exe" file. 
2. A keyboard was added to the system tray.
3. Open the "Configuration" window.
4. Installed and uninstalled keyboards are listed on the "Keyboard Layouts" tab.
5. Hotkeys works, which is mentioned on the "Hotkeys" tab.
6. Keyboard switched between languages by (Left-ALT + Shift).
7. The keyboard works well in Notepad and libreoffice. 
8. The feature works well in the Windows 10 and 11 OS environments. Thank you.

[keyman-server]

Changes in this pull request will be available for download in Keyman version 18.0.68-alpha