Integrate breadcrumbs

[odarriba]

This change adds support for breadcrumbs as a first-class field on our occurrences.

Breadcrumbs are now a way to store a list of strings indicating in which order they were added, so they can be used to track which code was executed and on which order. They are managed per-process (which in Phoenix means per-request in general)

• A new section in occurrence detail LiveView was added
• Some helper functions to add and list breadcrumbs were added
• The integration with Ash and Splode was updated to match the new system
• Some tests were added
• A new migration was added to create the new field

[odarriba]

Early review before doing docs and so on is appreciated @crbelaus can you take a look? 👀

[crbelaus]

I've pushed a small commit that adds a CustomException with bread crumbs so we can check how they interact with the breadcrumbs sent by ErrorTracker.add_breadcrumb/1.

[odarriba]

Ready to review again @crbelaus 🙌