Simplify quantified expressions over constants

[tautschnig]

Other simplification rules may turn the where-clause of a quantified expression into a (Boolean) constant. We can completely remove such quantified expressions so as not to distract back-ends that may special-case quantified expressions.

We saw such expressions when working on mlkem-native.

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[codecov]

Codecov Report

Attention: Patch coverage is 85.36585% with 6 lines in your changes missing coverage. Please review.

Project coverage is 80.37%. Comparing base (3c915eb) to head (6a8e038).

Files with missing lines	Patch %	Lines
src/solvers/flattening/boolbv_quantifier.cpp	28.57%	5 Missing ⚠️
src/util/simplify_expr_boolean.cpp	93.75%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #8608   +/-   ##
========================================
  Coverage    80.37%   80.37%           
========================================
  Files         1686     1686           
  Lines       206885   206928   +43     
  Branches        73       73           
========================================
+ Hits        166276   166312   +36     
- Misses       40609    40616    +7     

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[kroening]

It's unfortunately not that easy: The domain may be empty, and then ∀x.false is true, and ∃x.true is false.

[tautschnig]

It's unfortunately not that easy: The domain may be empty, and then ∀x.false is true, and ∃x.true is false.

Now fixed, and fixed the implementation in the propositional back-end as well.