Add SFTP password authentication tests for Commons VFS2

[VaishKumbhar]

What

Adds SftpPasswordAuthTest — new test class that verify SFTP password authentication via StaticUserAuthenticator in Commons VFS2.

Why

There is no dedicated test for SFTP password-based authentication. The existing SftpProviderTest relies on SftpTestServerHelper which accepts username == password and also allows UserAuthNone, so it does not specifically validate that StaticUserAuthenticator credentials are correctly propagated through the VFS2 SFTP provider.

How

• Each test spins up an inline embedded SSHD 0.8.0 server with a strict PasswordAuthenticator that only accepts a specific username/password pair.
• The server uses an explicit RSA 2048-bit host key instead of the SSHD 0.8.0 default DSA key, which is incompatible with Java 17+ (disabled legacy crypto algorithms).
• Server teardown uses a daemon thread with a 5-second timeout to prevent JVM hangs caused by SSHD 0.8.0 lingering sessions after failed authentication.
• Tests verify: resolving files, resolving folders (with and without trailing slash), and that wrong credentials produce a FileSystemException.

Test summary

Test	Description
testResolveFile	Connects with correct credentials, resolves a file, asserts it exists and is readable
testResolveFolder	Connects with correct credentials, resolves a directory
testResolveFolderWithTrailingSlash	Same as above with trailing slash in URI
testWrongCredentialsThrowsException	Connects with wrong credentials, asserts FileSystemException is thrown

[garydgregory]

Hello @VaishKumbhar

Thank you for the PR.

Please see my comments.

[garydgregory]

Hello @VaishKumbhar

Thank you for the PR.

Why should the order matter? Tests should be able to be run independently unless there is a bug causing side effects.

[garydgregory]

Please remove this comment, it doesn't document anything helpful IMO.