Add hidden option for User Roles

[kaos]

Description:

We would like to be able to select which roles are displayed when we set "Display Roles" to true in the User Interface section of the Layout settings.

This way, we are in control of which set of roles are displayed, without disclosing or advertising admins, moderators, owners and other default and needed user roles.

Steps to Reproduce:

1. Edit role, check/uncheck hidden flag (new feature)
2. Set Display Roles to true

Expected behavior:

Only those roles that have the hidden flag unchecked are displayed for users in the channels.

Actual behavior:

Currently, it is a all or nothing option to display no roles, or all roles.

[rocket-cat[bot]]

You don't have permission to execute this command add

[JSzaszvari]

@rocket-cat label add enhancement

[knrt10]

On it, will like to add this feature.