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

tests/unit/unit1395.c

@@ -62,9 +62,9 @@ UNITTEST_START
     { "test/this/../now", "test/now" },
     { "/1../moo../foo", "/1../moo../foo"},
     { "/../../moo", "/moo"},
-    { "/../../moo?andnot/../yay", "/moo?andnot/../yay"},
-    { "/123?foo=/./&bar=/../", "/123?foo=/./&bar=/../"},
-    { "/../moo/..?what", "/?what" },
+    { "/../../moo?", "/moo?"},
+    { "/123?", NULL},
+    { "/../moo/..?", "/" },
     { "/", NULL },
     { "", NULL },
     { "/.../", "/.../" },