feat(remoteaccess): support easier ssh port-forwarding for users

[reubenmiller]

Minor improvements to the c8y remoteaccess command to make it easier for users to start ssh port-forwarding (in various ways).

• c8y remoteaccess connect ssh - New -L <[bind_address:]port:host:hostport> flag which is used to pass to the ssh -L port-forwarding flag. But it also supports a short-form, -L <port> or -L <local_port>:<remote_port>

• c8y remoteaccess connect run - Inherits the parent's environment variables so it behaves the same as being run manually by the user in the shell

Examples

# Example 1: Setup ssh port forwarding, 127.0.0.1:1883 (remote) to 1883 (local)
c8y remoteaccess connect ssh --device 12345 --user admin -L 1883:127.0.0.1:1883

# Example 2: Setup ssh port forwarding, 127.0.0.1:1883 (remote) to 1883 (local)
c8y remoteaccess connect ssh --device 12345 --user admin -L 1883

# Example 3: Setup ssh port forwarding, 127.0.0.1:1883 (remote) to 1884 (local)
c8y remoteaccess connect ssh --device 12345 --user admin -L 1884:1883

# Example 4: Setup ssh port forwarding using custom ssh command call
c8y remoteaccess connect run --device rpi5-abcdef01 --configuration passthrough -- ssh -p %p -L 1885:127.0.0.1:1883 -o ServerAliveInterval=120 -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null root@127.0.0.1