Fixes: gh-8800
The `SmbFile.getName()` returns plain file name, not with a
sub-directory as it is expected by the `AbstractRemoteFileOutboundGateway`
for (S)FTP protocols
* Introduce `AbstractRemoteFileOutboundGateway.getFullFileName()`
with dir and file name concatenation by default (as it was before)
and override it in the `SmbOutboundGateway` to return the full path according this protocol.
* Fix `SmbOutboundGateway.enhanceNameWithSubDirectory()` to return an `SmbFile` instance
since it has all the info about remote file, include requested directory
* Fix `SmbOutboundGateway.getFilename()` to remove the trailing `/` in the dir name
since this is not what expected by the `AbstractRemoteFileOutboundGateway` logic
**Cherry-pick to `6.1.x`**
c7e3a7c24a