Secret generation for custom field

### Checks

- [x] I have read the Wiki, searched the open issues, and still think this is a new feature.

### Explain the problem clearly and succinctly:

I would like to request a possibility to generate a password for custom fields. For now, one can use a generation password functionality only for predefined field named "password" (icon of dices). But if I want to have some custom fields for other passwords, let's say, "password_2", "password_3", then I have to generate those secrets manually.

### Describe the solution you'd like:

That would be convenient to have the same icon of dices near those custom fields.

### Describe alternatives you've considered:

_No response_

### Additional context:

_No response_

Start by locating the predefined password field's dice control and the custom-field editor in the Android app. Trace how password generation is exposed for the named password field, then verify that custom password fields show the same control and produce generated secrets.

Written by the indexing model from the issue text.