Edit: Faster code action fixes

[umpox]

Part of #1544
Part of #1464

Description

"Ask Cody to Fix" is one of the most common command actions we currently have.

It makes sense to support this better instead of treating this like a normal "edit"

• Skip fetching context, from my personal testing it very rarely helps. Most information is contained within the error, or is part of relatedInformation attached to the diagnostic
  • We can start fetching more relevant context from sources directly related to the fix: Edit: Quality improvements: Add related fix context when available #1723
• Use a more targeted prompt preamble to address the task

Test plan

• Fixups without code actions (edit/document/edit with no selection)
• Fixups through code action (Ask Cody to Fix)

[valerybugakov]

Makes sense 👍 Looking forward to trying it together with #1723!