* Enable ExtendedDefaultRules for expressions in eval plugin (#1591)

* Add tests for fix#1591

* Add fix for #1954

* Remove dependency on xopt_set_unlessExplSpec.
Reason: It was breaking GHC 8.6.2 tests.

* Remove unnecessary comment.

Co-authored-by: Potato Hatsue <berberman@yandex.com>

Co-authored-by: Javier Neira <atreyu.bbb@gmail.com>
Co-authored-by: Potato Hatsue <1793913507@qq.com>
Co-authored-by: Potato Hatsue <berberman@yandex.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>