Fix 15042: ValueFlow: conditionally reassigned value should not be known (cppcheck-opensource#8899)

This refactors `ProgramMemory` so it can store a list of values.

A condition such as `x > 3` was recorded as the possible value 4 with a lower bound, and the executor then used it as if `x` were exactly 4. Nested conditions were decided wrongly, so branches were skipped and values leaked past or were lost before them. This what lead to the FP in 15042. 

Now it can understand these constraints better. As new values are added, it is resolved similar to `Token::addValue`.

Author: pfultz2

Makefile

@@ -646,7 +646,7 @@ $(libcppdir)/platform.o: lib/platform.cpp externals/tinyxml2/tinyxml2.h lib/conf
 $(libcppdir)/preprocessor.o: lib/preprocessor.cpp externals/simplecpp/simplecpp.h lib/checkers.h lib/config.h lib/errorlogger.h lib/errortypes.h lib/library.h lib/mathlib.h lib/path.h lib/platform.h lib/preprocessor.h lib/refthunk.h lib/settings.h lib/standards.h lib/suppressions.h lib/utils.h
 	$(CXX) ${INCLUDE_FOR_LIB} $(CPPFLAGS) $(CXXFLAGS) -c -o $@ $(libcppdir)/preprocessor.cpp
 
-$(libcppdir)/programmemory.o: lib/programmemory.cpp lib/astutils.h lib/calculate.h lib/checkers.h lib/config.h lib/errortypes.h lib/infer.h lib/library.h lib/mathlib.h lib/platform.h lib/programmemory.h lib/refthunk.h lib/settings.h lib/smallvector.h lib/sourcelocation.h lib/standards.h lib/symboldatabase.h lib/templatesimplifier.h lib/token.h lib/tokenlist.h lib/utils.h lib/valueflow.h lib/valueptr.h lib/vfvalue.h
+$(libcppdir)/programmemory.o: lib/programmemory.cpp lib/astutils.h lib/calculate.h lib/checkers.h lib/config.h lib/errortypes.h lib/infer.h lib/library.h lib/mathlib.h lib/platform.h lib/programmemory.h lib/refthunk.h lib/settings.h lib/smallvector.h lib/sourcelocation.h lib/standards.h lib/symboldatabase.h lib/templatesimplifier.h lib/token.h lib/tokenlist.h lib/utils.h lib/valueflow.h lib/valueptr.h lib/vf_common.h lib/vfvalue.h
 	$(CXX) ${INCLUDE_FOR_LIB} $(CPPFLAGS) $(CXXFLAGS) -c -o $@ $(libcppdir)/programmemory.cpp
 
 $(libcppdir)/regex.o: lib/regex.cpp lib/config.h lib/regex.h