[ddc] Handle deoptimized code patterns in compiler_new.dart after generational diffing is implemented

[Markzipan]

We've been emitting less optimal code to maintain compilation output consistency between hot reloaded and non-hot-reloaded code. However, certain core language features (constants, etc.) may require us to perform custom cross-generation diffing. In the advent of a diffing mechanism, we should un-deoptimize certain code patterns in compiler_new.dart:

• Instance fields only need a forwarding getter (with embedded initializer) when newly added
• SDK fields likely won't be hot reloaded and can be emitted without a value store + indirection getter (likely via a pragma)
• All fields only need implicit type checks when their type is updated
• RTI subtyping rules that implicitly refer to Object only need to be emitted for added/modified types
• Subtype check caches don't need to be cleared on the first generation
• We only need to tag functions that 1) are statically torn off or 2) have been reloaded from a statically torn off function.