clang-tidy: sync argument names in prototype and definition

Discovered with clang-tidy checker
`readability-inconsistent-declaration-parameter-name`.

Also:
- do not enforce the above because of inconsistencies still present
  between public API prototypes and definitions. (Also betwen man page
  protos, and man page examples, and other parts of the code, e.g.
  `easy` vs `curl` vs `d` vs `handle`) Perhaps subject for a future
  effort:
  https://github.com/curl/curl/actions/runs/22166472728/job/64094691653
- enable and fix `readability-named-parameter` where missing.

Refs:
https://clang.llvm.org/extra/clang-tidy/checks/readability/inconsistent-declaration-parameter-name.html
https://clang.llvm.org/extra/clang-tidy/checks/readability/named-parameter.html

Closes #20624

lib/sha256.c

@@ -452,14 +452,14 @@ static void my_sha256_final(unsigned char *out, void *ctx)
  * Returns CURLE_OK on success.
  */
 CURLcode Curl_sha256it(unsigned char *output, const unsigned char *input,
-                       const size_t length)
+                       const size_t len)
 {
   CURLcode result;
   my_sha256_ctx ctx;
 
   result = my_sha256_init(&ctx);
   if(!result) {
-    my_sha256_update(&ctx, input, curlx_uztoui(length));
+    my_sha256_update(&ctx, input, curlx_uztoui(len));
     my_sha256_final(output, &ctx);
   }
   return result;