[Feature] add migration support for Reviews to gitlab migration

[6543]

gitlab migration was introduced in #9084 but without GetReviews functionalety

after #11136 got merged ... check if the client now support reviews as described in:
#9084 (comment)

ref:

• https://docs.gitlab.com/ee/api/notes.html#merge-requests
• https://docs.gitlab.com/ee/user/project/merge_requests/merge_request_approvals.html

[6543]

@aqtrans ☝️

EDIT: I'll have a look at this