Re-compose NewIssueDropdown messages to support localizability

Relevant Slack thread: https://gitlab.slack.com/archives/C04P44Y06CS/p1734036310627679 (see screenshot in the internal note below)

Original merge request: Make NewIssueDropdown more versatile (!109863 - merged)

Problem

The English message Select project to create %{type} will be problematic for many non-English languages to make sense after translation, due to text being injected into other text via variable %{type}. The original code is removing the original text msgid "Select project to create issue" and instead is allowing the injection of natural language words into the already  existing Select project to create %{type}. The injectable keys are specified in this file, and are further stored somewhere in the .pot file, and they can be issue,  or merge request, or milestone.

Solution

Compose messages in full sentences:

• "Select project to create issue"
• "Select project to create merge request"
• "Select project to create milestone"

This is a re-composition suggestion only. For copy-editing the proposed 3 messages, it would be great to involve the technical writing team