[bugfix] move SQLite pragmas into connection string

[NyaaaWhatsUpDoc]

Description

As the title says really! Moves the SQLite connection pragmas into the connection string, just to ensure that all our connection preferences are set on every created new connection, considering that it's a little unclear what data is shared across SQLite connections. These are set using the _pragma URI query key as specified in the modernc.org/sqlite.Driver{}.Open() documentation.

An example of a connection string with this:
timestamp="01/09/2023 09:02:20.915" func=bundb.sqliteConn level=INFO msg="connected to SQLITE database with address file:/data/sqlite.db?_pragma=busy_timeout%28300000%29&_pragma=journal_mode%28WAL%29&_pragma=synchronous%28NORMAL%29&_pragma=cache_size%28-8192%29&_txlock=immediate"

Checklist

• I/we have read the GoToSocial contribution guidelines.
• I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
• I/we have performed a self-review of added code.
• I/we have written code that is legible and maintainable by others.
• I/we have commented the added code, particularly in hard-to-understand areas.
• I/we have made any necessary changes to documentation.
• I/we have added tests that cover new code.
• I/we have run tests and they pass locally with the changes.
• I/we have run go fmt ./... and golangci-lint run.

[tsmethurst]

excellent explanation, thanks for writing this up (and thanks from future you and me as well, reading this in two years, who would have had no idea why we did things this way if it wasn't for this comment)