Stunner - Show validation messages (Alerts)

Goal
Provide feedback about validation errors/warnings once saving, otherwise the process could be not saved but the end user gets not notifications at all.

Scope
This task should be kogito specific. For the BC we actually provide the Alerts panel.

Issue
When you model a process using VSCode and you use work items from a file in project. Some time the process is not saved.
You need to go into Properties panel and set the properties of servive (email, log) to some constant at the very least and your process gets saved.
I didn't see anything related in console.

Proposal
As the Alerts API is not yet available in our kogito fundation stuff, the proposal is to use bootstrap alerts in order to display the validation messages / alerts.

Acceptance criteria
Users should be able to see any validation errors or warnings, that could prevent the process from being saved.