rename \UTFviii@hexbyte into package namespace

PR was accepted but does not use this helper macro,
and so does not define it either

unicodedomino.sty

@@ -102,10 +102,15 @@
 }%
 \gdef\unicodedomino@hexseq#1#2\relax{%
  % display first octet
- \space "\UTFviii@hexbyte{`#1}%
+ \space "\unicodedomino@hexbyte{`#1}%
  % recursively handle remaining octets
  \ifx\relax#2\relax\else\unicodedomino@hexseq#2\relax\fi%
 }%
+% format a number as two-digit hex
+\gdef\unicodedomino@hexbyte#1{%
+ \ifnum#1<16 0\fi%
+ \UTFviii@hexnumber{#1}%
+}%
 
 % main handler
 \def\UTFviii@defined#1{%

unicodedomino_kernel_cosmetics.def

@@ -5,17 +5,11 @@
 %-
 % Improve error and warning formatting.
 
-%: https://github.com/latex3/latex2e/pull/82
-\ifx\UTFviii@hexbyte\@undefined%
- % format a number as two-digit hex
- \gdef\UTFviii@hexbyte#1{%
-  \ifnum#1<16 0\fi%
-  \UTFviii@hexnumber{#1}%
- }%
-
+%: https://github.com/latex3/latex2e/pull/82 (accepted)
+\ifx\unicodedomino@hexbyte\@undefined%
  % override message to give the byte in hex
  \def\UTFviii@invalid@err#1{%
-  \PackageError{inputenc}{Invalid UTF-8 byte "\UTFviii@hexbyte{`#1}}%
+  \PackageError{inputenc}{Invalid UTF-8 byte "\unicodedomino@hexbyte{`#1}}%
    \UTFviii@invalid@help%
  }%
 \fi%