Added Sendability conformance

[samdogg7]

Added Sendability conformance, where I could without modifying underlying code.

• Run make lint to check if there are any format errors (install swiftlint first)
• Run swift test to see if the tests pass.
• Write new tests for new functionality.
• Update documentation comments where applicable.

[samdogg7]

@nathanfallet I am wrapping SQLite.swift in my own module that I'd like to migrate over to Strict Concurrency. In my case, I particularly would like to mark Expression as Sendable. I added in a variety of Sendable conformances across the repository that didn't require changes to the underlying code. Larger coverage would be beneficial, but I think can be done iteratively.

[samdogg7]

@nathanfallet tests are failing due to iOS 18.0 being set as the version, looks like we only have 18.4 / 18.5 installed

[nathanfallet]

Try updating your branch with the main one. We handled this issue in a recently merged PR.