fix(crypto): password manager examples: use persistent actor

[fspreiss]

Adapts the password_manager and password_manager_with_metadata examples so that they work again with ICP Ninja, which recently upgraded to DFX 0.29.1, which ships with a new motoko compiler (0.16.1). The necessary changes for this were

• Declaring the actor as persistent and fixing the compiler issues

The Github workflow sets the DFX_VERSION environment variable, so that only this example uses the new DFX version 0.29.1. This also required to change the bind host from localhost to 127.0.0.1 as otherwise this new DFX version hits the following error:

Error: The replica returned an HTTP Error: Http Error: status 400 Bad Request, content type "text/plain; charset=utf-8", content: error: no_authority
details:
The request is missing the required authority information (e.g. 'Host' header).

The changes were tested in ICP Ninja with the following link:

Password manager:

Password manager with metadata:

[randombit]

lgtm