[ILM] Improve form error notification #87520
Description
The ILM policy form is quite long, especially with advanced settings expanded. If there is a form error, the current implementation makes it hard for the user to immediately know where the error is.
I think there is room for improvement within the JSON request flyout and when submitting the form.
For example, instead of showing this in the JSON flyout:
We could also list which fields have errors, something like this (copied from Index Templates):
For the form submission, a toast notification is displayed.
It might be helpful to add more details here as well, and possibly use a callout instead of the toast. It might also worth exploring adding a callout per phase.