patch 9.0.1177: AppVeyor uses some older tools

Problem:    AppVeyor uses some older tools.
Solution:   Switch to Visual Studio 2022 and Python 3.11. (Christopher
            Plewright, closes #11793)

.appveyor.yml

@@ -1,6 +1,6 @@
 version: "{build}"
 
-image: Visual Studio 2015
+image: Visual Studio 2022
 
 skip_tags: true
 
@@ -16,8 +16,21 @@ matrix:
   fast_finish: true
 
 before_build:
-  # Use Visual Studio 2015 compiler tools (default is 2012)
-  - '"C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" x86_amd64'
+  # Use latest compiler tools (Visual Studio 2022)
+  - setlocal ENABLEDELAYEDEXPANSION
+  - call ver
+  - set "VSWHERE=%ProgramFiles(x86)%\Microsoft Visual Studio\Installer\vswhere.exe"
+  - >
+    if exist "%VSWHERE%" (
+    for /f "usebackq delims=" %%i
+    in (`"%VSWHERE%" -products * -latest -property installationPath`) 
+    do (set "VCVARSALL=%%i\VC\Auxiliary\Build\vcvarsall.bat")
+    )
+  - > 
+    if not exist "%VCVARSALL%" (
+    set "VCVARSALL=%ProgramFiles(x86)%\Microsoft Visual Studio 14.0\VC\vcvarsall.bat"
+    )
+  - call "%VCVARSALL%" x64
 
 build_script:
   - ci/appveyor.bat
@@ -25,7 +38,7 @@ build_script:
 test_script:
   - cd src/testdir
     # Testing with MSVC gvim
-  - path C:\Python35-x64;%PATH%
+  - path C:\Python311-x64;%PATH%
   - nmake -f Make_mvc.mak VIMPROG=..\gvim
   - nmake -f Make_mvc.mak clean
     # Testing with MSVC console version