Obey enforced password setting for share by mail

[tobiasKaminsky]

• Android @tobiasKaminsky
• Desktop @camilasan
• iOS @marinofaggiana
• Server Cleanup share by mail a bit #21692

There will be sharebymail->password->enforced starting with NC20.
So we can rely on this and directly show a password prompt, if needed.

[skjnldsv]

Relevant #24364