CBQI BV choice expressions (#1296)

CBQI BV choice expressions (#1296)

* Use Hilbert choice expressions for cbqi bv. Failing in debug due to TNode issues currently.

* Minor

* Make unique bound variables for choice functions in BvInstantor, clean up.

* Incorporate missing optimizations

* Clang format

* Unused field.

* Minor

* Fix, add regression.

* Fix regression.

* Fix bug that led to incorrect cleanup of instantiations.

* Add missing regression

* Improve handling of choice rewriting.

* Fix

* Clang format

* Use canonical variables for choice functions in cbqi bv.

* Add regression

* Clang format.

* Address review.

* Clang format