sshnp: add -u option to specify username to use if sshnpd is not sharing it

[gkc]

Is your feature request related to a problem? Please describe.

from @cconstab

sshnp shoukd have a -u option to specify the username if the sshnpd was not sharing it.
This is a bug/oversight in sshnp right now.

Describe the solution you'd like

• add an optional -u option in SSHNP.createArgParser with full option name remote-user-name, description something like, "user name to use in the ssh session on the remote host"
• in SSHNP, change remoteUserName from late final String remoteUsername to String? remoteUserName
• add optional remoteUserName parameter to SSHNP constructor to allow remoteUserName to be supplied, and supply the parsed
• in SSHNP.init - do not call fetchRemoteUserName if a remoteUserName has already been supplied

Describe alternatives you've considered

No response

Additional context

Either wait for #201 to be merged to trunk, or make a new branch based on that PR's branch

[VJag]

@purnimavenkatasubbu Can you work on this ticket? @srieteja can help if you need.

[purnimavenkatasubbu]

PR merged to trunk. Closing this issue as fixed.