Feature Request: Allow for storing hashed caching sha2 credentials in static auth server

[dbussink]

Feature Description

It's possible today to store hashed credentials with the static auth server in a file when using mysql_native_password. This allows for the credentials to be not human readable as they are one way hashed.

When using caching_sha2_password, this currently only works with a plain text password in the file. We should also allow for storing those values hashed as well so they are not in plain text anymore.

Use Case(s)

Better security for passwords when using caching_sha2_password with the static auth server.