Kibana needs to display better error message to user if user tries to save metric threshold alert without all the values

[bhavyarm]

Kibana version: 7.7.0 BC8

Elasticsearch version: 7.7.0 BC8

Server OS version: Cloud

Browser version: chrome latest

Browser OS version: OS X

Original install method (e.g. download page, yum, from source, etc.): from staging

Describe the bug: If User clicks on save while creating metric threshold alert without adding values or actions - Kibana displays "params invalid error"

We need some validation to let the user know whats happening.

[simianhacker]

This might be fixed in BC9. I will confirm and post a response.