Drivers should generally allow "dangling" statements and record readers

### What feature or improvement would you like to see?

https://github.com/apache/arrow-adbc/issues/3713
https://github.com/apache/arrow-adbc/issues/3135#issuecomment-3064168884

We should allow you to close a statement even if the record reader is not drained, and close a connection even if statements are not closed. Currently this is considered unsafe and various bindings guard against this. Instead the driver should be prepared and invalidate the statement/readers.

I think, however, the API user should still be expected to Release the statement/reader to avoid leaking memory. But leaking memory is better than crashing.

Start by reading the linked issues #3713 and #3135, then trace how drivers handle closing statements, record readers, and connections. Done means drivers safely invalidate still-open dependent objects when their parent is closed, while users remain responsible for releasing them to avoid memory leaks.

Written by the indexing model from the issue text.