Add option to create issue from last issue for Feast users

[jonathonherbert]

What's changed?

Gives an option to use the last available issue prior to the date of the issue being inserted when creating Feast issues.

Implementation notes

This is accomplished by finding the most recent issue prior to the selected date, and recreating it as a Skeleton, which strips unique information (e.g. uuids) from it. (The Skeleton types are there to create issues from templates.) The issue skeleton is then inserted as normal.

How to test

• The automated tests should pass. They cover the happy path, and ensure that we don't get any duplicate data from issues prior to the select issue. They also cover the case where an issue isn't found. (This should be rare!)
• Have a play! Try creating an issue where no prior issue exists – you should get a reasonable error message:

Checklist

General

• [x] 🤖 Relevant tests added
• [x] ✅ CI checks / tests run locally
• [ ] 🔍 Checked on CODE

Client

• [x] 🚫 No obvious console errors on the client (i.e. React dev mode errors)
• [x] 🎛️ No regressions with existing user interactions (i.e. all existing buttons, inputs etc. work)
• [x] 📷 Screenshots / GIFs of relevant UI changes included