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

src/tool_operate.h

@@ -27,7 +27,7 @@
 
 #include "tool_cb_hdr.h"
 #include "tool_cb_prg.h"
-#include "tool_sdecls.h"
+#include "tool_cfgable.h"
 
 struct per_transfer {
   /* double linked */

src/tool_sdecls.h

@@ -128,10 +128,4 @@ typedef enum {
   SANITIZE_ERR_LAST /* never use! */
 } SANITIZEcode;
 
-/*
- * Complete struct declarations which have OperationConfig struct members,
- * just in case this header is directly included in some source file.
- */
-#include "tool_cfgable.h"
-
 #endif /* HEADER_CURL_TOOL_SDECLS_H */