Fixes: #9909
Issue link: https://github.com/spring-projects/spring-integration/issues/9909
The `SftpSession.close()` closes `sftpClient` and its `clientSession` unconditionally.
At the same time the `DefaultSftpSessionFactory.isSharedSession` is expected to expose only a single shared client.
When this `DefaultSftpSessionFactory` is used concurrently, there is a chance that one thread would close
that shared client and another won't be able to interact due to `clientSession` is closed.
* Fix `SftpSession` accepting an `isSharedClient` flag and doing nothing in the `close()` if client is shared.
* Propagate `isSharedSession` state down to the `SftpSession` from the `DefaultSftpSessionFactory`
* Closed shared client and its `clientSession` in the `DefaultSftpSessionFactory.destroy()`
(cherry picked from commit 2df9611dde)
# Conflicts:
# spring-integration-sftp/src/test/java/org/springframework/integration/sftp/session/SftpSessionFactoryTests.java
0fe58fd699