[DO] Document operations that prevent eviction

[iglesiasbrandon]

Summary

Documents additional pending operations that prevent Durable Object eviction. This draft explains the behavior, billing impact, and reason for the change before release.

• Documents service binding fetches, requests to other Durable Objects, and container.monitor() as operations that prevent eviction.
• Clarifies the 15-minute period for each operation and how later operations can extend time in memory.
• Updates lifecycle, pricing, container monitoring, and WebSocket guidance to use consistent language.
• Adds a changelog entry and timeline diagram showing the behavior.
• Leaves the compatibility and release dates for follow-up after they are finalized.

Screenshots (optional)

Documentation checklist

• Is there a changelog entry (guidelines)? If you don't add one for something awesome and new (however small) — how will our customers find out? Changelogs are automatically posted to RSS feeds, the Discord, and X.
• The change adheres to the documentation style guide.

[iglesiasbrandon]

Replaced by #33454 so the branch can use the repository's deploy preview workflow.