Support password hashes in Change Passwords API

[jkakavas]

We should allow users to call our Change Passwords API by passing a hash of the desired password value instead of the actual password itself. We support this already for the Put Users API . Use cases for this can include:

• Cleartext password doesn't need to traverse the network
• Performance for changing passwords for multiple users where password hashing can be offloaded before (rather than during) the actual request.
• We have a valid use case for this in the Security On by Default project: Set elastic password and generate enrollment token for initial node #75310

relates: #34729

[elasticmachine]

Pinging @elastic/es-security (Team:Security)

[jkakavas]

This was implemented in #75500