Removes invalid characters 0xfffe and 0xffff when cleaning XML

[karenhanson]

This removes two additional forbidden characters when cleaning XML to be output by the XMLHandler in Utils.encodeContent() and Utils.encodeValue(). If you leave these characters in the XML, it generates an invalid character message during validation of JHOVE output.

Relates to #877

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +16.85% 🎉

Comparison is base (8a4d1ce) 30.15% compared to head (a3f3c23) 47.00%.
Report is 3 commits behind head on integration.

Additional details and impacted files

@@                Coverage Diff                 @@
##             integration     #878       +/-   ##
==================================================
+ Coverage          30.15%   47.00%   +16.85%     
- Complexity           651     1100      +449     
==================================================
  Files                 57       57               
  Lines               9079     9079               
  Branches            1622     1622               
==================================================
+ Hits                2738     4268     +1530     
+ Misses              5965     4280     -1685     
- Partials             376      531      +155     

Files Changed	Coverage Δ
...src/main/java/edu/harvard/hul/ois/jhove/Utils.java	62.16% <ø> (+41.44%)	⬆️

... and 33 files with indirect coverage changes

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[karenhanson]

This appears to address #880, which has a sample file attached that can be used for testing.

Update Oct 30, 23: from discussion on #880, this fixes the error message on that ticket, but does not address the underlying issue, which appears to be to do with how the bits are read in. The file on that ticket can be used to test though.