Remove SysvarSerialize trait dependency

[grod220]

Related: anza-xyz/agave#10672

Removes impl SysvarSerialize for StakeHistory and stops constructing StakeHistory test accounts via solana-account sysvar helpers.

These call sites keep the repo tied to upstream APIs that require SysvarSerialize, causing lockstep version coupling between solana-sysvar, solana-account, and solana-stake-interface.

Next steps

• Agave
  • Stop creating StakeHistory sysvar accounts through create_account::(...) and use direct bincode serialization instead.
  • rRplace SysvarSerialize-bound StakeHistory paths in program-test / banks-client
• Mollusk
  • Update the sysvar account construction path so StakeHistory can be handled without a SysvarSerialize bound
• Stake repo
  • Once those upstream pieces land, re-run the stake program against the updated dependency graph to confirm no remaining StakeHistory-specific SysvarSerialize coupling remains

[joncinque]

Beautiful, thank you!