rewrote squeeze in Rascal with reified classes

[jurgenvinju]

• this passes the type-checker now with the latest release; it had an intricate issue with type parameters of the type[..] constructor that was resolved.
• it reuses the #[a-z] character class notation instead of strings for the second parameter of squeeze
• it reuses @DavyLandman's visit-style pure Rascal implementation of squeeze
• this PR also fixes several serious issues (unimplemented unicode and ascii escapes, and problems with unicode characters) in character-class reification code. These issues were triggered by the tests of the squeeze function.
• have to remove some accidental commits in documentation strings of the vis::Graphs module before we merge.
• also fixes char-class type reificiation does something wrong for high surrogate/low surrogate pairs #2009
• also fixes the notation for literal symbols and case-insensitive literal symbols (all the same as character classes)

[codecov]

Codecov Report

Attention: Patch coverage is 17.85714% with 23 lines in your changes missing coverage. Please review.

Project coverage is 49%. Comparing base (1690da7) to head (2b24936).
Report is 18 commits behind head on main.

Files with missing lines	Patch %	Lines
...org/rascalmpl/values/parsetrees/SymbolFactory.java	17%	23 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##              main   #2002   +/-   ##
=======================================
  Coverage       49%     49%           
- Complexity    6309    6322   +13     
=======================================
  Files          664     664           
  Lines        59633   59584   -49     
  Branches      8648    8640    -8     
=======================================
+ Hits         29486   29497   +11     
+ Misses       27938   27877   -61     
- Partials      2209    2210    +1     

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[DavyLandman]

LGTM

[jurgenvinju]

This now also fixes the other issues identified in #2009 and some more because of better testing (especially now character escaping works the same for literals, ci-iterals and character classes). The \f case has to be fixed in vallang.

[jurgenvinju]

@PaulKlint Davy has looked at it and the PR I merged into this was also reviewed already. Many more tests were added; I think the compiler will not have issue with those.

[DavyLandman]

@jurgenvinju

The \f case has to be fixed in vallang.

it has been, just not released a new version of vallang yet.

[jurgenvinju]

Check!