build: enable missing OpenSSF-recommended warnings, with fixes

https://best.openssf.org/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C++.html
as of 2023-11-29 [1].

Enable new recommended warnings (except `-Wsign-conversion`):

- enable `-Wformat=2` for clang (in both cmake and autotools).
- add `CURL_PRINTF()` internal attribute and mark functions accepting
  printf arguments with it. This is a copy of existing
  `CURL_TEMP_PRINTF()` but using `__printf__` to make it compatible
  with redefinting the `printf` symbol:
  https://gcc.gnu.org/onlinedocs/gcc-3.0.4/gcc_5.html#SEC94
- fix `CURL_PRINTF()` and existing `CURL_TEMP_PRINTF()` for
  mingw-w64 and enable it on this platform.
- enable `-Wimplicit-fallthrough`.
- enable `-Wtrampolines`.
- add `-Wsign-conversion` commented with a FIXME.
- cmake: enable `-pedantic-errors` the way we do it with autotools.
  Follow-up to d5c0351055 #2747
- lib/curl_trc.h: use `CURL_FORMAT()`, this also fixes it to enable format
  checks. Previously it was always disabled due to the internal `printf`
  macro.

Fix them:

- fix bug where an `set_ipv6_v6only()` call was missed in builds with
  `--disable-verbose` / `CURL_DISABLE_VERBOSE_STRINGS=ON`.
- add internal `FALLTHROUGH()` macro.
- replace obsolete fall-through comments with `FALLTHROUGH()`.
- fix fallthrough markups: Delete redundant ones (showing up as
  warnings in most cases). Add missing ones. Fix indentation.
- silence `-Wformat-nonliteral` warnings with llvm/clang.
- fix one `-Wformat-nonliteral` warning.
- fix new `-Wformat` and `-Wformat-security` warnings.
- fix `CURL_FORMAT_SOCKET_T` value for mingw-w64. Also move its
  definition to `lib/curl_setup.h` allowing use in `tests/server`.
- lib: fix two wrongly passed string arguments in log outputs.
  Co-authored-by: Jay Satiro
- fix new `-Wformat` warnings on mingw-w64.

[1] 56c0fde389/docs/Compiler-Hardening-Guides/Compiler-Options-Hardening-Guide-for-C-and-C%2B%2B.md

Closes #12489

src/tool_getparam.c

@@ -2337,7 +2337,7 @@ ParameterError getparameter(const char *flag, /* f or -long-flag */
         config->file_clobber_mode = toggle ? CLOBBER_ALWAYS : CLOBBER_NEVER;
         break;
       }
-      /* FALLTHROUGH */
+      FALLTHROUGH();
     case 'o': /* --output */
       /* output file */
     {
@@ -2640,7 +2640,7 @@ ParameterError getparameter(const char *flag, /* f or -long-flag */
       switch(*nextarg) {
       case '+':
         nextarg++;
-        /* FALLTHROUGH */
+        FALLTHROUGH();
       default:
         /* If-Modified-Since: (section 14.28 in RFC2068) */
         config->timecond = CURL_TIMECOND_IFMODSINCE;