Provide multiple validate clauses for base16 (#15337)

It is consistent with the other implementations.

Author: PJUllrich

lib/elixir/lib/base.ex

@@ -376,6 +376,26 @@ defmodule Base do
 
     defp unquote(validate_name)(<<>>), do: true
 
+    defp unquote(validate_name)(<<c1, c2, c3, c4, c5, c6, c7, c8, rest::binary>>) do
+      unquote(valid_char_name)(c1) and
+        unquote(valid_char_name)(c2) and
+        unquote(valid_char_name)(c3) and
+        unquote(valid_char_name)(c4) and
+        unquote(valid_char_name)(c5) and
+        unquote(valid_char_name)(c6) and
+        unquote(valid_char_name)(c7) and
+        unquote(valid_char_name)(c8) and
+        unquote(validate_name)(rest)
+    end
+
+    defp unquote(validate_name)(<<c1, c2, c3, c4, rest::binary>>) do
+      unquote(valid_char_name)(c1) and
+        unquote(valid_char_name)(c2) and
+        unquote(valid_char_name)(c3) and
+        unquote(valid_char_name)(c4) and
+        unquote(validate_name)(rest)
+    end
+
     defp unquote(validate_name)(<<c1, c2, rest::binary>>) do
       unquote(valid_char_name)(c1) and
         unquote(valid_char_name)(c2) and