Event Definition New Feature: Add a bulk edit feature

## What?

A bulk editing feature for Event Definitions would reduce the needed time create useful alerts. Currently, each Event Definition has to be edited manually.

## Why?

With the introduction of SIGMA rules and curated alerts, a customer will have hundreds of Event Definitions. If a customer or the developer team like SecCon wants to include an important custom field like user_name or an IP field, the user or developer has to create the keys in each Event Definition.

A bulk edit function of the fields tab would reduce the time to modify all event definitions from many hours to a few minutes.

Maybe it also makes sense to have this feature for Notifications, adding Streams and Stream Categories, modify execution times (if it does not already exist.)


## Your Environment

* Graylog Version: 6.2
* OpenSearch Version:
* MongoDB Version:
* Operating System:
* Browser version: