refactor(session replay) use custom IDB store for event management

[kwalker3690]

Summary

This PR migrates the SR SDK off of idb-keyval to a more robust IDB schema that will allow us more flexibility in the implementation of Targeted Replay Capture.

export interface SessionReplayDB extends DBSchema {
  sessionCurrentSequence: {
    key: number;
    value: {
      sessionId: number;
      events: Events;
    };
  };
  sequencesToSend: {
    key: number;
    value: SendingSequencesIDBInput;
    indexes: { sessionId: number };
  };
}

The current replay being captured will add events to sessionCurrentSequence. Once that list is large enough, as well as on blur, we will move that list to sequencesToSend, which will automatically provide it a sequence id. Then the list will be sent to the backend, upon a successful API response we will delete the list from sequencesToSend. In this model, IDB will be the source of truth for events (previously, they were also stored in memory).

https://www.loom.com/share/d3a5b4bc26b84f2d92d49458e9f7794f

Checklist

• Does your PR title have the correct title format?
• Does your PR have a breaking change?: no

[lewgordon-amplitude]

Looks good overall. Nothing hard blocking, but I think some suggestions might make the code trimmer.