Merge branch '433174-add-a-custom-vuex-store' into 'master'

Add a custom store for Pending promotion tab in member management pages

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/149094



Merged-by: Peter Hegman <phegman@gitlab.com>
Approved-by: Angelo Gulina <agulina@gitlab.com>
Approved-by: Peter Hegman <phegman@gitlab.com>
Reviewed-by: Angelo Gulina <agulina@gitlab.com>
Reviewed-by: Kos Palchyk <kpalchyk@gitlab.com>
Co-authored-by: Kos Palchyk <kpalchyk@gitlab.com>