This commit:
1. Combines all domain (non-atree) payloads into
   one account (non-atree) payload per account.
2. Combines all domain (atree) storage maps into
   one account (atree) storage map per account.
3. Uses on-the-fly (OTF) migration when an
   account is modified (write ops).

Currently, accounts store data on-chain under pre-defined domains,
such as "storage".  Each domain requires domain payload
(8-byte non-atree payload) and domain storage map payload (atree payload).
Also, each payload requires ~2 mtrie nodes (~2x96 byte overhead).

New domains were added in Cadence 1.0 and domain payloads count
increased to 150 million on Sept. 4 (was 80 million pre-spork).
Nearly 25% of total payloads on-chain are 8-byte domain payloads.
Each account on mainnet has an average of ~4 domain payloads and
~4 domain storage maps.

This commit creates 1 account (non-atree) payload and 1 account
(atree) storage map per account, eliminating all domain (non-atree)
payloads and domain storage maps for that given account.

Based on preliminary estimates using Sept. 17, 2024 mainnet state,
this approach can:
- eliminate mtrie nodes: -425 million (-28.5%)
- reduce payload count: -174 million (also -28.5%)

This commit also includes on-the-fly migration so we can see
improvements to accounts that have write activity without requiring
downtime.  Given this, we won't see the full benefits/impact until
all accounts (including idle accounts) are eventually migrated
(e.g. using full migration or other means).

…regsiters

This is for completeness.