Move control character checking to FU::Validate, deprecate FU::Util::utf8_decode()

URI, JSON and formdata decoding no longer checks for control characters,
but FU::Validate now rejects control characters by default. This
decouples semantic validation from format parsing and gives better
control over when control characters are allowed.

t/query.t

@@ -7,9 +7,6 @@ is_deeply
     query_decode('a&a&%c3%be=%26%3d%c3%be&a=3'),
     { a => [ builtin::true, builtin::true, 3 ], "\xfe" => "&=\xfe" };
 
-ok !eval { query_decode('%10'); 1 };
-like $@, qr/Invalid control character/;
-
 ok !eval { query_decode('a=%fe%83%bf%bf%bf%bf%bf%0a'); 1 };
 like $@, qr/does not map to Unicode/;