[Snapshot Performance] account_meta should be part of funk_rec

[ripatel-fd]

Storing account metadata on the heap instead of the record table incurs significant overhead.
All Solana accounts (>99% of funk records) have account metadata.
But a significant amount of Solana accounts only has metadata but no data (system accounts).

Therefore moving account_meta into funk_rec

• Improves cache locality (saves the need for DRAM fetches of account data, likely already hot due to cache line readahead on funk_rec).
• Reduces the amount of heap allocations done for mainnet snapshots by hundreds of millions, for all those system accounts.

However, it makes funk index footprint worse due to 47 bytes of padding ... 🤔