Add msgctxt support for proper context in pot files
<!--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> - [Label this issue](https://contributors.gitlab.com/manage-issue?action=label&projectId=278964&issueIid=20203) - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=20203) </details> <!--IssueSummary end--> Our `pot` files should use the `msgctxt` field to store context rather than prefixing the message. This will allow context to be rendered correctly in Crowdin. Crowdin has a field beneath the string in the translation view where context is shown. It is always empty for GitLab because we don't use `msgctxt` Reference: http://pology.nedohodnik.net/doc/user/en_US/ch-poformat.html#sec-podisamb
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