[WIP] HTTP Client Config

[stevensJourney]

Overview

This PR allows configuring the Ktor networking client we use for PowerSync connections.

This currently allows for a broad range of configuration, including:

• Installing additional Ktor plugins. E.g the Logging pluging or Custom plugins.
• Customising request headers etc via the DefaultRequest plugin.

Todos And Open Questions

• Verify Websocket logging - this seems to currently be quite limited.
• Gauge the impact of exposing and depending on Ktor in our public SyncOptions API
• Confirm if there is an actual use case for providing an existing Ktor client, versus hooking in to the configuration process of a new client.
• Investigate formatting changes (might be an issue with my dev setup)

The Ktor Logging plugin has been added to the Hello-PowerSync demo. A sample log of the HTTP request headers is below

2025-07-23 09:25:33.516 11804-11844 System.out              com.powersync.demos                  I  Authorization=[Token token]
2025-07-23 09:25:33.516 11804-11844 System.out              com.powersync.demos                  I  User-Agent=[PowerSync Kotlin SDK v1.3.0 (Android 29)]
2025-07-23 09:25:33.516 11804-11844 System.out              com.powersync.demos                  I  Accept-Charset=[UTF-8]
2025-07-23 09:25:33.516 11804-11844 System.out              com.powersync.demos                  I  Accept=[*/*]
2025-07-23 09:26:03.535 11804-11844 System.out              com.powersync.demos                  I  Response headers:
2025-07-23 09:26:03.536 11804-11844 System.out              com.powersync.demos                  I  access-control-allow-origin=[*]
2025-07-23 09:26:03.536 11804-11844 System.out              com.powersync.demos                  I  access-control-expose-headers=[Content-Type]
2025-07-23 09:26:03.536 11804-11844 System.out              com.powersync.demos                  I  connection=[keep-alive]
2025-07-23 09:26:03.536 11804-11844 System.out              com.powersync.demos                  I  content-length=[2419]
2025-07-23 09:26:03.536 11804-11844 System.out              com.powersync.demos                  I  content-type=[application/json; charset=utf-8]
2025-07-23 09:26:03.536 11804-11844 System.out              com.powersync.demos                  I  date=[Wed, 23 Jul 2025 07:26:42 GMT]
2025-07-23 09:26:03.536 11804-11844 System.out              com.powersync.demos                  I  keep-alive=[timeout=72]
2025-07-23 09:26:03.536 11804-11844 System.out              com.powersync.demos                  I  vary=[Origin]

[simolus3]

This looks nice 👍

One thing I'm wondering about is if we can use this to remove the createClient field in SyncStream and PowerSyncDatabaseImpl (since we now have a proper option for this). I've added those for tests, but it looks like we can now pass the test engine via connection options instead.
(and then as a fallback when the engine option is null, use defaultHttpClient from the companion or just inline the HttpClient call)

[simolus3]

Also we should remember to make ktor an API dependency in Gradle for this.

(and carefully evaluate the impact that has on the generated Swift headers)