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/multiif.h

@@ -47,7 +47,7 @@ void Curl_multi_connchanged(struct Curl_multi *multi);
 /* Internal version of curl_multi_init() accepts size parameters for the
    socket, connection and dns hashes */
 struct Curl_multi *Curl_multi_handle(uint32_t xfer_table_size,
-                                     size_t hashsize,
+                                     size_t ev_hashsize,
                                      size_t chashsize,
                                      size_t dnssize,
                                      size_t sesssize);