Preprocess and convert C1 controls to their 7 bit equivalent (#7340)

C1 control characters are now first converted to their 7 bit equivalent.
This allows us to unify the logic of C1 and C0 escape handling. This
also adds support for SOS/PM/APC string.

* Unify the logic for C1 and C0 escape handling by converting C1 to C0
  beforehand. This adds support for various C1 characters, including
  IND(8/4), NEL(8/5), HTS(8/8), RI(8/13), SS2(8/14), SS3(8/15),
  OSC(9/13), etc. 
* Add support for SOS/PM/APC escape sequences. Fixes #7032
* Use "Variable Length String" logic to unify the string termination
  handling of OSC, DCS and SOS/PM/APC. This fixes an issue where OSC
  action is successfully dispatched even when terminated with non-ST
  character. Introduced by #6328, the DCS PassThrough is spared from
  this issue. This PR puts them together and add test cases for them.

References:
https://vt100.net/docs/vt510-rm/chapter4.html
https://vt100.net/emu/dec_ansi_parser

Closes #7032
Closes #7317

.github/actions/spell-check/dictionary/dictionary.txt

@@ -20937,6 +20937,8 @@ apay
 Apayao
 APB
 APC
+Apc
+apc
 APDA
 APDU
 APE
@@ -383889,6 +383891,7 @@ sorus
 sorva
 sory
 SOS
+Sos
 sos
 Sosanna
 so-seeming