containertool should have a `--default-password-from-stdin` option

For cases where using an environment variable is not suitable, it should be possible to pipe the password into `containertool`.

Start at the containertool command entry point and inspect how the existing environment-variable password option is parsed. Add the requested --default-password-from-stdin behavior so a piped password can be used, then verify the command accepts input from standard input without requiring the environment variable.

Written by the indexing model from the issue text.