Move bitvector types into util/bitvector_types.h

[kroening]

• Each commit message has a non-empty body, explaining why the change was made.
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• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• n/a Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
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[codecov]

Codecov Report

Merging #5898 (c09297c) into develop (81d075d) will increase coverage by 0.00%.
The diff coverage is 98.67%.

@@           Coverage Diff            @@
##           develop    #5898   +/-   ##
========================================
  Coverage    73.09%   73.09%           
========================================
  Files         1428     1430    +2     
  Lines       155075   155076    +1     
========================================
+ Hits        113357   113358    +1     
  Misses       41718    41718           

Impacted Files	Coverage Δ
...java_bytecode/java_bytecode_internal_additions.cpp	100.00% <ø> (ø)
jbmc/src/java_bytecode/remove_exceptions.cpp	95.58% <ø> (ø)
...rams/remove_virtual_functions_without_fallback.cpp	98.52% <ø> (ø)
...s/variable-sensitivity/abstract_pointer_object.cpp	76.66% <ø> (ø)
...ses/variable-sensitivity/abstract_value_object.cpp	95.43% <ø> (ø)
...s/variable-sensitivity/interval_abstract_value.cpp	81.96% <ø> (ø)
src/ansi-c/c_nondet_symbol_factory.cpp	100.00% <ø> (ø)
src/ansi-c/padding.cpp	93.36% <ø> (ø)
src/cpp/cpp_is_pod.cpp	100.00% <ø> (ø)
src/cpp/cpp_type2name.cpp	89.13% <ø> (ø)
... and 93 more

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