[KO Classic Phonemizers] Apply Korean sandhi rules to Classic phonemizers

[lottev1991]

With this PR, the Korean UTAU phonemizers will apply Korean sandhi rules to Hangeul lyrics. Some of the classic phonemizers already have the sandhi rules applied properly with KoreanPhonemizerUtil, so these are not affected.

Affected phonemizers:

• KO VCV;
• KO CVCCV;
• KO CVC (I think some of the old code could be deleted, but I haven't yet properly looked into that, because I'm afraid of breaking things. I might one day);
• KO to JA.

[lottev1991]

Apologies for the failing checks, I got this error:

Determining projects to restore...
/home/runner/work/OpenUtau/OpenUtau/OpenUtau/OpenUtau.csproj : error NU1903: Warning As Error: Package 'System.Text.Json' 7.0.2 has a known high severity vulnerability, https://github.com/advisories/GHSA-hh2w-p6rv-4g7w
  Restored /home/runner/work/OpenUtau/OpenUtau/OpenUtau.Core/OpenUtau.Core.csproj (in 9.94 sec).
  Restored /home/runner/work/OpenUtau/OpenUtau/OpenUtau.Plugin.Builtin/OpenUtau.Plugin.Builtin.csproj (in 9.94 sec).
  Failed to restore /home/runner/work/OpenUtau/OpenUtau/OpenUtau/OpenUtau.csproj (in 9.97 sec).
Error: Process completed with exit code 1.

Is there anything I can do about that, or that can be done about it? I'm kinda lost here... I keep rerunning checks but it doesn't seem to be working.

[oxygen-dioxide]

Please sync the latest code from stakira/OpenUtau to your fork, and the tests will pass