KEYCLOAK-18423 user friendly name for user profile attributes

[velias]

Based on top of the PR #8179 to prevent merge conflicts as it changes same files, so should be merged after it (I'll rebase this PR once parent is merged).
Few notes:

• I used advancedMsg freemarker method to render field name in login theme (used in verify-profile.ftl for now) as it supports i18n replacers in an east way. The method is now added always to the freemarker context beside common msg (before it was added for one page type only)
• possibility to set displayName added to the Admin GUI editor, and also shown in the list of attributes so admin has common overview
• Attribute names are correctly rendered into new account console error messages
• User update error messages rendering kept as is for the Admin Console - attribute name (no display name) is shown here still as it is also used in attributes list in GUI. Expected improvement in new Admin console as user profile page will be cleared. But I moved admin message rendering code out of ValidationException into Admin REST API resource to clean internal architecture a bit.
• tests implemented both for JSON config parsing and to verify correct rendering of the names in verify-profile.ftl
• created UserProfileBeanBase with code which can be reused for all login templates working with user profile (registration, user update)

@pedroigor hope given changes make sense to you