feat(proposer): SQLite changes

[ratankaliani]

In SQLite, there can only be one write operation at a time.

Previously, this caused database is locked errors, which did not cause downtime on the application, but are good to handle more correctly.

Create a writeClient that uses setMaxOpenConnections to provide a Mutex for write queries, and a readClient with several open connections.

Optimizations from: https://kerkour.com/sqlite-for-servers, used https://entgo.io/docs/sql-integration/ for the ent integration.