Add confirmation when importing multiple projects

Related issues: #25193 (closed) #26727 (closed)

What does this MR do?

This MR adds count to "Import all projects" button (now will be "Import X repositories button") and confirmation modal to prevent accidential importing tons of repositories

Video

New_Project___GitLab

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done