* Add shutdown signal handling
Revert periodic sync interval change
Revert keep-alive interval change
CLI: Add disconnect command
SDK: Add scaffolding for is_started, shutdown()
Simplify instance init
* Rebase on savage-async-ws branch
* Avoid waiting when shutdown signal is received in the sync loop
* Directly use shutdown signal in background threads
* Acquire is_started lock at the very beginning of start()
* Fix cargo clippy warnings
* Update RN generator (kt): set bindingLiquidSdk to null on disconnect()
* Update RN generator (swift): set bindingLiquidSdk to nil on disconnect()
* Startup: only run foreground sync() if this could be the first run
* Start a sync() in background, before regular sync() loop
* Remove ensure_started check from start()
* Add bindings for disconnect()
* Remove foreground sync condition from startup
* Simplify background sync loop
