Add support to forward TLS passphrase to go-connections

[marcosnils]

the go-connections library recently included an option to set TLS passphrase when decrypting private keys (docker/go-connections#35). It'd be nice if this option could be added to the CLI as well so users don't have to type their passphrase each time they want to execute a command with an encrypted key.

I can send the PR if you think this should go in. I propose the flag to be --tlspassphrase

@vdemeester WDYT?

[vdemeester]

Seems good to me
/cc @cyli @dnephin @n4ss

[bsousaa]

Support of password encrypted TLS was deprecated. Please see https://github.com/docker/cli/blob/v23.0.0-rc.3/docs/deprecated.md#support-for-encrypted-tls-private-keys. Corresponding PR #3218