Use Shamir as KeK when migrating from auto-seal to shamir (#8172)

* Use Shamir as KeK when migrating from auto-seal to shamir

* Use the correct number of shares/threshold for the migrated seal.

* Fix log message

* Add WaitForActiveNode to test

* Make test fail

* Minor updates

* Test with more shares and a threshold

* Add seal/unseal step to the test

* Update the logic that prepares seal migration (#8187)

* Update the logic that preps seal migration

* Add test and update recovery logic

Co-authored-by: ncabatoff <nick.cabatoff@gmail.com>
Co-authored-by: Brian Kassouf <briankassouf@users.noreply.github.com>