feat(event cache): sqlite persistent storage for the event cache :sunglasses:

[bnjbvr]

This implements the following parts of https://github.com/matrix-org/matrix-rust-sdk/issues/3280#issuecomment-2488679063:

• implement a sqlite backend for the event cache store
• save events into the store as they come from sync
• reload data from the store and use it to prefill the linked chunks for all rooms

For getting a nice demo in the multiverse client, a few shortcuts have been taken in the last commit, but these should be relatively easy to solve.

The demo shows the following:

• open the client for the first time
• observe the focused room is mostly empty
• I manually back-paginate, getting some events back from the server
• then, close the client
• reopen it
• observe the events are still there (they were persisted on disk).

https://github.com/user-attachments/assets/50983dc7-0d53-4363-b8ee-9b68c363995a

More to come next week.