[Account Storage Maps] Refactor migration

[turbolent]

Depends on #3678

Description

• Simplify the bookkeeping in V2: only keep a simple map, an ordered map is unnecessary
• Simplify the domain register migration to allow migration of a single account
• For now, bring back the automatic migration of written-to accounts during commit.
  We'll keep discussing this in the upcoming sync with the Execution team.

---

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[turbolent]

The update of the bookkeeping is the same as before: Make V2 aware of the new account storage map, so it is not re-loaded, and consider the account no longer as V1. From what I can see this should be sufficient, but it's good to double check this is sufficient. @fxamacker

[SupunS]

Similar to the other PR, I don't have a lot of context on the business logic. So I mostly reviewed for the general Go code.

[turbolent]

Merging into #3678 to have all changes needed to pass CI in one PR, as discussed in #3678 (comment)