Upgrade to Rails 7.0.5

[phillmv]

What it says on the tin!

This PR:

• Handles the new default YAML safe_loading behaviour
• Adds a new migration to transition any existing notebooks to the new merge script
• Deals with a bunch of deprecation notices, silences noisy tests
• Fixes some changes that happened to the behaviour of transaction blocks
• Fiddles with webpacker to fix some weird behaviour that turned out to be mostly caching related.

[phillmv]

There is some import bug that has something to do with file timestamps that happens inside Linux but not on MacOS that I simply do not have the time to debug. So alas, today is not the day I get to fix my Actions CI env.