clang-tidy: check misc-header-include-cycle, fix in internal headers

Also opt-out `curl/curl.h` because it includes `curl/mprintf.h`, which
in turn includes `curl/curl.h` for `CURL_EXTERN`. Not changeable in
public headers to remain compatible. (Somehow only triggered for
examples.)

Ref: https://clang.llvm.org/extra/clang-tidy/checks/misc/header-include-cycle.html

Closes #20645

lib/functypes.h

@@ -23,8 +23,6 @@
  * SPDX-License-Identifier: curl
  *
  ***************************************************************************/
-#include "curl_setup.h"
-
 /* defaults:
 
    ssize_t recv(int, void *, size_t, int);