Support for hot reload in DDC

[sigmundch]

This is a meta issue to track any individual work towards support for hot reload in DDC.

The table below is just an approximation. It is meant to be updated periodically as we figure out plans, steps, and complete tasks.

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• Testing preparations:
  • (in progress) test harness for coverage and faster team iteration
  • add suite of test cases from VM tests
• Representation changes
  • (in progress) Disentangle libraries from modules
  • Changes to library representation to allow updates to top-levels and classes
  • Enable new runtime type representation by default
  • Ensure indirection: all member access, including fields, can be updated
  • Changes to class representation to stop capturing type parameters via closures
  • Changes to scoping and hoisting: push down hoisted variables inside method bodies
• Hot reload mechanics
  • Add internal state-management of hot reloads
  • Updating library and class objects in-place
  • Replacing field initializers to ensure existing objects reflect the correct value of newly added fields
  • Detection of rejection cases
• Debugging support
  • Version management and source-map support
• Integration
  • Unify module systems
  • Add hot reload workflows into dwds and flutter-tools