feat: add state persistence for LiteSVM

[kc1116]

Summary

• Adds a litesvm-persistence crate that can save and restore full LiteSVM state to/from files or byte buffers using bincode serialization
• Feature-gated persistence-internal on litesvm exposes internal getters/setters without polluting the public API
• Two-pass account loading during restore avoids MissingAccount errors when upgradeable BPF programs are inserted before their ProgramData accounts
• CRC32 checksums detect file/data corruption, atomic temp-file writes prevent corrupt snapshots on crash

Persisted state

Accounts, feature set, compute budget, fee structure (including compute_fee_bins), blockhash, airdrop keypair, sigverify/blockhash_check/log_bytes_limit settings, and transaction history with capacity.

Restore ordering

with_compute_budget() is called before with_builtins() so runtime environments are created with the correct budget. All accounts are bulk-inserted first (set_account_no_checks), then sysvar + program caches are rebuilt in a single rebuild_caches() pass.

Test plan

• 21 round-trip tests covering: basic accounts, multiple accounts, sysvars, config flags, blockhash, airdrop keypair, transaction history, BPF program execution after restore, custom compute budget, custom fee structure, history capacity, bytes API, double round-trip, full default round-trip, error cases (nonexistent file, corrupted data), CRC32 checksum verification (bytes + file)
• 2 doc-tests compile successfully
• All existing litesvm tests still pass

🤖 Generated with Claude Code