patch 8.2.1317: MS-Windows tests on AppVeyor are slow

Problem:    MS-Windows tests on AppVeyor are slow.
Solution:   Use GitHub Actions. (Ken Takata, closes #6569)
diff --git a/ci/appveyor.bat b/ci/appveyor.bat
index 590c48a..164d7bc 100644
--- a/ci/appveyor.bat
+++ b/ci/appveyor.bat
@@ -5,48 +5,32 @@
 cd %APPVEYOR_BUILD_FOLDER%
 
 cd src
-echo "Building MinGW 32bit console version"
-set PATH=c:\msys64\mingw32\bin;%PATH%
-mingw32-make.exe -f Make_ming.mak GUI=no OPTIMIZE=speed IME=yes ICONV=yes DEBUG=no FEATURES=%FEATURE% || exit 1
-.\vim -u NONE -c "redir @a | ver |0put a | wq" ver_ming.txt
-:: Save vim.exe before Make clean, moved back below.
-copy vim.exe testdir
-mingw32-make.exe -f Make_ming.mak clean
-
-:: Build Mingw huge version with python and channel support, or
-:: with specified features without python.
-echo "Building MinGW 32bit GUI version"
-if "%FEATURE%" == "HUGE" (
-    mingw32-make.exe -f Make_ming.mak OPTIMIZE=speed CHANNEL=yes GUI=yes IME=yes ICONV=yes DEBUG=no PYTHON_VER=27 DYNAMIC_PYTHON=yes PYTHON=C:\Python27 PYTHON3_VER=35 DYNAMIC_PYTHON3=yes PYTHON3=C:\Python35 FEATURES=%FEATURE% || exit 1
-) ELSE (
-    mingw32-make.exe -f Make_ming.mak OPTIMIZE=speed GUI=yes IME=yes ICONV=yes DEBUG=no FEATURES=%FEATURE% || exit 1
-)
-.\gvim -u NONE -c "redir @a | ver |0put a | wq" ver_ming_gui.txt
-
 :: Filter out the progress bar from the build log
 sed -e "s/@<<$/@<< | sed -e 's#.*\\\\r.*##'/" Make_mvc.mak > Make_mvc2.mak
 
 echo "Building MSVC 64bit console Version"
-nmake -f Make_mvc2.mak CPU=AMD64 OLE=no GUI=no IME=yes ICONV=yes DEBUG=no FEATURES=%FEATURE% || exit 1
-:: The executable is not used
-nmake -f Make_mvc2.mak clean
+nmake -f Make_mvc2.mak CPU=AMD64 ^
+    OLE=no GUI=no IME=yes ICONV=yes DEBUG=no ^
+    FEATURES=%FEATURE% || exit 1
 
 :: build MSVC huge version with python and channel support
 :: GUI needs to be last, so that testing works
 echo "Building MSVC 64bit GUI Version"
 if "%FEATURE%" == "HUGE" (
-    nmake -f Make_mvc2.mak DIRECTX=yes CPU=AMD64 CHANNEL=yes OLE=no GUI=yes IME=yes ICONV=yes DEBUG=no PYTHON_VER=27 DYNAMIC_PYTHON=yes PYTHON=C:\Python27-x64 PYTHON3_VER=35 DYNAMIC_PYTHON3=yes PYTHON3=C:\Python35-x64 FEATURES=%FEATURE% || exit 1
+    nmake -f Make_mvc2.mak CPU=AMD64 ^
+        OLE=no GUI=yes IME=yes ICONV=yes DEBUG=no POSTSCRIPT=yes ^
+        PYTHON_VER=27 DYNAMIC_PYTHON=yes PYTHON=C:\Python27-x64 ^
+        PYTHON3_VER=35 DYNAMIC_PYTHON3=yes PYTHON3=C:\Python35-x64 ^
+        FEATURES=%FEATURE% || exit 1
 ) ELSE (
-    nmake -f Make_mvc2.mak CPU=AMD64 OLE=no GUI=yes IME=yes ICONV=yes DEBUG=no FEATURES=%FEATURE% || exit 1
+    nmake -f Make_mvc2.mak CPU=AMD64 ^
+        OLE=no GUI=yes IME=yes ICONV=yes DEBUG=no ^
+        FEATURES=%FEATURE% || exit 1
 )
 .\gvim -u NONE -c "redir @a | ver |0put a | wq" ver_msvc.txt
 
-:: Restore vim.exe, tests will run with this.
-move /Y testdir\vim.exe .
-echo "version output MinGW"
-type ver_ming.txt
-echo "version output MinGW GUI"
-type ver_ming_gui.txt
-echo "version output MVC"
+echo "version output MSVC console"
+.\vim --version
+echo "version output MSVC GUI"
 type ver_msvc.txt
 cd ..