Pass vault name and input type (password, MFA) to askpass

[tgyurci]

It would be useful if the askpass helper would know the vault name which the user wants to unlock and the requested secret is password or MFA token without parsing it from the prompt message. It can be used for querying the password/token from password stores, for example from macOS Keychain by an askpass script.

The vault name and input type could be passed as additional parameters or in environment variables.