[Ingest Pipelines] Add prompt for unsaved changes in processors

[SoniaSanzV]

Summary

When an user is working on adding a processor and click outside the side flyout before saving the changes, their work gets lost. This is especially annoying if the user is working on a complex processor and clicks out of the window unintentionally.

Steps to reproduce

• Navigate to Ingest Pipelines
• Click create Create Pipeline
• Click Add a processor
• Add some processor and some data. Click outside the flyout before saving the changes.

This PR introduced a similar change for the entire form.

[elasticmachine]

Pinging @elastic/kibana-management (Team:Kibana Management)