Fix escalation policy model edit button bugs

What does this MR do and why?

This MR aims to solve some bugs in the edit form of the escalation policy.

Related issues

• #376697 (closed)

Problems

• Button disabled but clickable when editing an existing policy
• When text changes, the button didn't enable, until input lost focus
• When you save changes, then edit again, the state is not saved, so it allows you to save again despite no changes being made.
• Other problems in Linux and Firefox were reported. I couldn't reproduce them, but I think this MR solve them as well.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.