feat(ENG-282): Add InitializeAccount2 CPI to INIT-VAULT

[alnoki]

Changes

1. Add InitializeAccount2 struct to interface/src/token.rs
   with discriminant (u8) and proprietor (Address) fields,
   and inject its discriminant, account count, and seed count
   constants into common/token.s
2. Add rent pointer and initialize_account_2_data fields to
   RegisterMarketFrame, with corresponding RENT,
   INIT_ACCT_2_DATA, INIT_ACCT_2_DISC, and
   INIT_ACCT_2_PROPRIETOR constant group entries
3. Store the Rent sysvar account pointer on the frame during
   REGISTER-MARKET parsing (after address validation)
4. Extend INIT-VAULT to invoke InitializeAccount2 CPI after
   CreateAccount, setting up vault (writable), mint (readonly),
   and Rent sysvar (readonly) as CPI accounts, with the market
   PDA address as the token account proprietor
5. Add cpi[2] is_signer/is_writable preconditions to
   INIT-VAULT (zero-initialized, never modified)
6. Add InitializeAccount2 to size_of_group! in
   interface/src/memory.rs
7. Update check_vault! test macro to unpack and verify token
   account fields (mint, proprietor, amount, state) using
   spl_token_interface::state::Account
8. Add Token 2022 extension mints (TransferFeeConfig,
   TransferHook) to happy path tests so the two vaults in
   the all-2022 case have different GetAccountDataSize results
9. Add spl-token-2022-interface and solana-program-pack
   workspace dependencies for extension types and Pack trait
10. Rename discriminator to discriminant across interface,
    assembly, and docs for consistency

[linear]

ENG-282