patch 9.1.1365: MS-Windows: compile warnings and too many strlen() calls

Problem:  MS-Windows: compile warnings and too many strlen() calls  in
          os_mswin.c
Solution: refactor os_mswin.c and fix the warning (John Marriott)

This change does the following:

- Fix compile warnings (clang 20.1.3) in `mch_libcall()`:
```
os_mswin.c:902:21: warning: cast from 'MYSTRPROCSTR' (aka 'char *(*)(char *)') to 'MYSTRPROCINT' (aka 'int (*)(char *)') converts to incompatible function type [-Wcast-function-type-mismatch]`
  902 |                     retval_int = ((MYSTRPROCINT)ProcAdd)((LPSTR)argstring);`
      |                                   ^~~~~~~~~~~~~~~~~~~~~`
os_mswin.c:914:21: warning: cast from 'MYINTPROCSTR' (aka 'char *(*)(int)') to 'MYINTPROCINT' (aka 'int (*)(int)') converts to incompatible function type [-Wcast-function-type-mismatch]`
  914 |                     retval_int = ((MYINTPROCINT)ProcAddI)(argint);`
      |                                   ^~~~~~~~~~~~~~~~~~~~~~`
2 warnings generated.
```

- Refactor `stat_impl()` to remove call to `STRLEN()` (via `STRCAT()`).

- Refactor `Messaging_WndProc()`, `enumWindowsGetServer()` and
  `serverSendToVim()` to remove calls to `STRLEN()`.

- Use `string_T` to store field `name` in `struct charset_pair` and
  `struct quality_pair`. This means we can dispense with some calls to
  `STRLEN()`.

- Use `ARRAY_LENGTH()` macro to determine end of array in
  `charset_id2name()` and `quality_id2name()` to be consistent with the
  rest of the code base.

closes: #17222

Signed-off-by: John Marriott <basilisk@internode.on.net>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1365,
 /**/
     1364,
 /**/