REL: release notes v4.0.0

[tangkong]

Description

Release the notes!

Motivation and Context

The time to tag is transpiring (TTTT)

How Has This Been Tested?

N/A

Where Has This Been Documented?

This is docs

Pre-merge checklist

• Code works interactively
• Code contains descriptive docstrings, including context and API
• New/changed functions and methods are covered in the test suite where possible
• Code has been checked for threading issues (no blocking tasks in GUI thread)
• Test suite passes locally
• Test suite passes on GitHub Actions
• Ran docs/pre-release-notes.sh and created a pre-release documentation page
• Pre-release docs include context, functional descriptions, and contributors as appropriate

[ZLLentz]

The conda test suites have a pretty dramatic error but it isn't particularly related to what we've done here

[tangkong]

As a reminder for myself, this fails with the qt6 issue thanks to pcdsdevices. Typhos itself does not depend on matplotlib, nor does it pull in bluesky