Replace import confirmation modal with hover message
<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=352707) </details> <!--IssueSummary end--> ### Problem to solve Based on the conversation in https://gitlab.com/gitlab-org/gitlab/-/merge_requests/80434#note_839581269, as a follow-up #344559 and #344558 we should replace the confirmation modal used to inform user's about how to enable various import methods. Currently the import bitbucket and import from gitlab buttons are available under the right conditions, clicking the button results in a modal popping up to provide instructions on how to enable the features. | Before MR | Current appearance | |---|---| |![Screen_Shot_2022-02-14_at_1.28.00_pm](/uploads/8bc926287ccf0ed8b414eed8e78b3e3a/Screen_Shot_2022-02-14_at_1.28.00_pm.png)|![Screen_Shot_2022-02-14_at_1.06.10_pm](/uploads/ff76eb22b0dead7ad797dd05245ee630/Screen_Shot_2022-02-14_at_1.06.10_pm.png)| ### Proposal We should: * [ ] Display the buttons in a _disabled_ state when the features need to be enabled * [ ] Provide a popover with the relevant link to the help information * [ ] ~~Is it possible to standardize the import interaction UI when clicking the various buttons~~ moved to https://gitlab.com/gitlab-org/gitlab/-/issues/353522 * [ ] Add additional specs for the bitbucket button: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/80434#note_842295015 Related to #344559 and #344558
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