build: tidy-up MSVC CRT warning suppression macros

- curl_setup.h: replace `_CRT_SECURE_NO_DEPRECATE` with
  `_CRT_SECURE_NO_WARNINGS`, which seems to be the preferred,
  more recent macro for this. Also syncing with libssh2.
  They are equivalent for curl sources with the supported compilers.
- cmake: stop setting `_CRT_SECURE_NO_DEPRECATE` globally for examples.
- examples: suppress CRT deprecation warnings on a per-file basis.
  To make it work when compiling examples out of curl's build systems.
  Use `_CRT_SECURE_NO_WARNINGS`.
- examples: document the functions requiring `_CRT_SECURE_NO_WARNINGS`.
- examples/block_ip: delete superfluous `_CRT_SECURE_NO_WARNINGS`.
- examples/block_ip: limit `_CRT_NONSTDC_NO_DEPRECATE` to MSVC.
- examples/log_failed_transfers: fix to set `_CRT_SECURE_NO_WARNINGS`
  before headers and limit to MSVC.
- curl_setup.h: document which SDKs support `_CRT_NONSTDC_NO_DEPRECATE`.

Closes #19175

docs/examples/http2-serverpush.c

@@ -25,6 +25,12 @@
  * HTTP/2 server push
  * </DESC>
  */
+#ifdef _MSC_VER
+#ifndef _CRT_SECURE_NO_WARNINGS
+#define _CRT_SECURE_NO_WARNINGS  /* for _snprintf(), fopen() */
+#endif
+#endif
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -32,14 +38,14 @@
 /* curl stuff */
 #include <curl/curl.h>
 
-#if defined(_MSC_VER) && (_MSC_VER < 1900)
-#define snprintf _snprintf
-#endif
-
 #ifndef CURLPIPE_MULTIPLEX
 #error "too old libcurl, cannot do HTTP/2 server push!"
 #endif
 
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#define snprintf _snprintf
+#endif
+
 static FILE *out_download;
 
 static void dump(const char *text, unsigned char *ptr, size_t size, char nohex)