Fix recurring crash when Connection deinitializes

[vjymisal0]

Problem

Fixes #1276.

In Connection.deinit, calling ry? close() invokes sqlite3_close(handle). If any prepared statements, blobs, or backup operations remain unfinalized when the Connection goes out of scope, sqlite3_close() returns SQLITE_BUSY. Because the call is wrapped in ry?, the failure is swallowed, leaving the connection open and in an unmanaged state, which can trigger crashes or memory corruption when lingering statements are subsequently deallocated.

Solution

Use sqlite3_close_v2(handle) directly in Connection.deinit:

1. SQLite's sqlite3_close_v2 is explicitly designed for reference-counted / GC environments. If open statements remain, it puts the connection into a 'zombie' state and automatically destroys the database connection when the last statement finalizes.
2. It bypasses queue.sync during deinit, avoiding deadlock or re-entrancy issues when deallocation occurs on arbitrary dispatch queues.

Testing

Existing unit and integration test suites cover connection lifecycle. Swift tests verified against operator and connection changes.

[jberkel]

no longer needed