Move shortenString helper file to be used as a general helper

**What is this about?**

Currently, shortenString helper lives in `app/util/notifications/methods/common.ts`. However, there are no use-cases for shortenString until recent redesign confirmation PRs.

This issue is to move shortenString to a new filepath to be used at a higher scope

**Stakeholder review needed before the work gets merged**

- [ ] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

Start by reading app/util/notifications/methods/common.ts and tracing shortenString references, including the redesign confirmation PRs mentioned in the issue. Determine the appropriate higher-scope location before moving the helper, then update its consumers and verify the existing checks pass. Done means the helper is available from its new path without breaking current uses.

Written by the indexing model from the issue text.