replace custom model checker with chiseltest formal verify command (#2075)

* replace custom model checker with chiseltest formal verify command

* integration-tests can make use of chiseltest

This is a compromise solution to avoid issues
with binary compatibility breaking changes in chisel3.

* ci: move integration tests into separate job

* run integration tests only for one scala version

* ci: install espresso for integration tests

* Update build.sbt

Co-authored-by: Jack Koenig <jack.koenig3@gmail.com>

Co-authored-by: Jack Koenig <jack.koenig3@gmail.com>