Revise the New Diffs blueprint

What does this MR do and why?

Closes #439077 (closed)

Tasks

These were uncovered in a pairing session announced to all the members of the initiative:

• Update non goals

• Proposal > Accessibility: move to design and implementation details.

• Add section between Motivation and Proposal: Process

  • Move Workspace & artefacts there

• Promote Definitions to top level after Proposal and before Design and Implement.

• Good place for Metrics? Move between Proposal and design and implementation. Title: Acceptance Criteria

  • Add Time to First Diff visible section

• Design and implementation details:

  • Create section Accessibility
  • Move the Front end children to Accessibility

• Alternative Solutions:

  • List what we tried so far
  • SSR all at once
  • Virtual Scrolling
  • Batch diffing

• Proposed changes:

  • Frontend (Design A): move to acceptance criteria > Frontend (new section)
  • High level implementation: nothing until we discuss in the call.
  • Proposal (Design B):
  • Check for incorrections (Phil)
  • "The new-diffs approach changes that by doing the following:"
    • update the wording
  • Move to Alternative Solutions
  • Design & Implementation Details (Design B)
  • Perhaps remove. Covered by the Time to First Diff. (Not sure of the exact numbers)
  • Overview
  • Update to mention streaming. (Reword)
  • Show a graph how the requests will be spread across a full page lifecycle.
  • [ ]
  • Move to Design and Implementation Details
  • Static and dynamic separation
  • Performance optimisations

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