windows: fix UWP builds, add GHA job

Add new job to test building for UWP (aka `CURL_WINDOWS_APP`).

Fix fallouts when building for UWP:
- rand: do not use `BCryptGenRandom()`.
- cmake: disable using win32 LDAP.
- cmake: disable telnet.
- version_win32: fix code before declaration.
- schannel: disable `HAS_MANUAL_VERIFY_API`.
- schannel: disable `SSLSUPP_PINNEDPUBKEY`
  and make `schannel_checksum()` a stub.
  Ref: e178fbd40a #1429
- schannel: make `cert_get_name_string()` a failing stub.
- system_win32: make `Curl_win32_impersonating()` a failing stub.
- system_win32: try to fix `Curl_win32_init()` (untested).
- threads: fix to use `CreateThread()`.
- src: disable searching `PATH` for the CA bundle.
- src: disable bold text support and capability detection.
- src: disable `getfiletime()`/`setfiletime()`.
- tests: make `win32_load_system_library()` a failing stub.
- tests/server/util: make it compile.
- tests/server/sockfilt: make it compile.
- tests/lib3026: fix to use `CreateThread()`.

See individual commits for build error details.

Some of these fixes may have better solutions, and some may not work
as expected. The goal of this patch is to make curl build for UWP.

Closes #13870

src/tool_filetime.c

@@ -41,7 +41,7 @@ int getfiletime(const char *filename, struct GlobalConfig *global,
 /* Windows stat() may attempt to adjust the unix GMT file time by a daylight
    saving time offset and since it's GMT that is bad behavior. When we have
    access to a 64-bit type we can bypass stat and get the times directly. */
-#if defined(_WIN32)
+#if defined(_WIN32) && !defined(CURL_WINDOWS_APP)
   HANDLE hfile;
   TCHAR *tchar_filename = curlx_convert_UTF8_to_tchar((char *)filename);
 
@@ -95,7 +95,7 @@ void setfiletime(curl_off_t filetime, const char *filename,
 /* Windows utime() may attempt to adjust the unix GMT file time by a daylight
    saving time offset and since it's GMT that is bad behavior. When we have
    access to a 64-bit type we can bypass utime and set the times directly. */
-#if defined(_WIN32)
+#if defined(_WIN32) && !defined(CURL_WINDOWS_APP)
     HANDLE hfile;
     TCHAR *tchar_filename = curlx_convert_UTF8_to_tchar((char *)filename);