[RFC] Stage 0: Introducing Event Entities Fields

[romulets]

Overview

This RFC proposes Event Entities fields. This will benefit security use cases related to investigation worfklows

Checklist

• Have you signed the contributor license agreement?
• Have you followed the contributor guidelines?
• For proposing substantial changes or additions to the schema, have you reviewed the RFC process?
• If submitting code/script changes, have you verified all tests pass locally using make test?
• If submitting schema/fields updates, have you generated new artifacts by running make and committed those changes?
• Is your pull request against main? Unless there is a good reason otherwise, we prefer pull requests against main and will backport as needed.
• Have you added an entry to the CHANGELOG.next.md?

[mjwolf]

Suggested change

	* Stage 0: https://github.com/elastic/ecs/pull/2384
	* Stage 0: https://github.com/elastic/ecs/pull/2385

the correct PR number