Interactive prompts from 'helm registry login' (username/password/token)
and the signing-key passphrase prompts in 'helm package' and
'helm plugin package' are printed to stdout. Anyone capturing stdout
(scripts, pipelines) gets prompt text mixed into the output; the
docker/kubectl/oras convention is to keep prompts on stderr so stdout
stays machine-readable.
Also in registry login's readLine:
- the term.DisableEcho error was silently discarded, so a failure to
disable echo would print the password to the terminal with no
warning; it now returns an error instead
- echo handling is only attempted when stdin is actually a terminal,
so piped input (e.g. 'echo pw | helm registry login ...' without
--password-stdin) keeps working as before
Signed-off-by: Mukul <nmukul32@gmail.com>