urlapi: cleanups

- move host checks together
- simplify the scheme parser loop and the end of host name parser
- avoid itermediate buffer storing in multiple places
- reduce scope for several variables
- skip the Curl_dyn_tail() call for speed
- detect IPv6 earlier and skip extra checks for such hosts
- normalize directly in dynbuf instead of itermediate buffer
- split out the IPv6 parser into its own funciton
- call the IPv6 parser directly for ipv6 addresses
- remove (unused) special treatment of % in host names
- junkscan() once in the beginning instead of scattered
- make junkscan return error code
- remove unused query management from dedotdotify()
- make Curl_parse_login_details use memchr
- more use of memchr() instead of strchr() and less strlen() calls
- make junkscan check and return the URL length

An optimized build runs one of my benchmark URL parsing programs ~41%
faster using this branch. (compared against the shipped 7.88.1 library
in Debian)

Closes #10935

lib/setopt.c

@@ -115,7 +115,11 @@ static CURLcode setstropt_userpwd(char *option, char **userp, char **passwdp)
   /* Parse the login details if specified. It not then we treat NULL as a hint
      to clear the existing data */
   if(option) {
-    result = Curl_parse_login_details(option, strlen(option),
+    size_t len = strlen(option);
+    if(len > CURL_MAX_INPUT_LENGTH)
+      return CURLE_BAD_FUNCTION_ARGUMENT;
+
+    result = Curl_parse_login_details(option, len,
                                       (userp ? &user : NULL),
                                       (passwdp ? &passwd : NULL),
                                       NULL);