Fix issue with project dropdown translation for languages without pluralisation

What does this MR do?

Splits up the "projects selected" string in the /-/analytics/cycle_analytics view.

This is to address an issue with pulling the translations for this string in Chinese (!21921 (closed)).

With the way this string is currently structured the variable projectName cannot be supplied in Chinese as the target language has one plural form so there is no option to supply a secondary string.

This MR splits up the two strings so that the one that requires translation is independent of the project name.

Screenshots

Failing pipeline: https://gitlab.com/gitlab-org/gitlab/-/jobs/381880899

Errors in `/builds/gitlab-org/gitlab/locale/zh_CN/gitlab.po`:
63   CycleAnalytics|%{projectName}
64     Failure translating to zh_CN: can't convert Hash into Integer

Entry with issues in Crowdin:

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