tidy-up: C and CI

- drop redundant casts for `CURL_UNCONST()` pointers (Windows).
- GHA/linux: delete redundant/dupe `-g` C flag in memory sanitizer job.
  Spotted-by: Daniel Stenberg
- examples/http2-upload: drop local macro.
- examples/http2-upload: drop leading underscore from union name.
- examples/http2-upload: drop interim macro.
- tests/server/util: reapply patch lost in a rebase.
- sync `main()` declarations across the codebase.

Closes #22559

docs/examples/ftp-wildcard.c

@@ -97,7 +97,7 @@ static size_t write_cb(char *buff, size_t size, size_t nmemb, void *cb_data)
   return written;
 }
 
-int main(int argc, const char **argv)
+int main(int argc, const char *argv[])
 {
   /* curl easy handle */
   CURL *curl;